GANT211 MIDTERM
Located at the posterior cranial fossa
Functions:
Control balance and posture coordination of skilled voluntary movements
Movement planning
Command to move
Overlies the posterior side of the pons & medulla
Shallow anterior cerebellar incisure superiorly
Deeper incisure inferiorly
Superficial layer: gray matter
Inner layer: white matter called the arbor vitae
Symmetrical hemispheres connected by vermis
Furrows called fissures: anterior and posterolateral
Longitudinal Division:
Lateral zone
Intermediate zone
Vermis
Nuclei:
Fastigeal nucleus: most medial; contains small & large multipolar neurons
Globose nucleus: contains small & large multipolar neurons
Emboliform nucleus: wedge-shaped mass composed of large multiform nucleus with dendrites
Dentate nucleus: largest & most lateral; appears as convoluted mass resembling the olivary nucleus
Lobes:
Anterior lobe: control posture, locomotion & fine motor coordination
Posterior lobe: control posture, locomotion & fine motor coordination
Flocculonodular lobe: control balance & eye movement
Fissures:
Primary fissure
Posterolateral fissure
Horizontal fissure
Archicerebellum: oldest; regulation of equilibrium and posture; receives input from the vestibular nerve and medial vestibular nuclei
Paleocerebellum: associated with proprioceptive & exteroceptive inputs from head and body; regulates muscle tone
Neocerebellum: largest and newest; associated with neocortex of cerebrum, pontine nuclei, & inferior olivary nucleus of medulla; muscle coordination of phasic movements
Superior cerebellar peduncle (Brachium conjunctivum): connects cerebellum to midbrain; forms the largest cerebellar efferent bundle; fibers arise from dentate, emboliform & globose nuclei
Middle cerebellar peduncle (brachium pontis): connects cerebellum to pons; fibers arise from pons thru ponto-cerebellar tract; consist of afferent fibers
Inferior cerebellar peduncle (brachium restiformins): connects the cerebellum with the medulla; conveys unconscious proprioceptive & exteroceptive information to the cerebellum
Cerebellum found below the occipital lobe of the cerebrum & behind the medulla & pons of the brain stem & within the posterior cranial fossa
Separated from these lobes by the tentorium cerebelli, a tough layer of dura mater
50% of the total number of neurons in the brain
Considered a motor structure, because cerebellar damage leads to impairments in motor control & posture
Cerebellum modifies the motor commands of the descending pathways to make movements more adaptive & accurate
Maintenance of balance & posture
Coordination of voluntary movements
Motor learning
Cognitive functions such as language
Ventricles are a communicating network of cavities
Choroid plexus produces cerebrospinal fluid (CSF)
Ventricles are lined with specialized connective tissue called ependyma
Ventricles are connected by tight junctions forming the blood-CSF barrier
Lateral ventricle: found inside the cerebral hemispheres; divided into central portion and lateral extensions or horns
Third ventricle: small, slit-like cavity in the center of the diencephalon between the two thalami; continuous with the cerebral aqueduct of Sylvius
Fourth ventricle: diamond-shaped cavity located between the pons and the cerebellum
The meninges are membranous coverings of the brain and spinal cord.
Layers of the meninges:
Pachymeninx (dura mater)
Composed of dense, fibrous tissues
Contains periosteal layer and meningeal layer
Dural venous sinuses located between the two layers
Leptomeninges
Arachnoid mater
Located between the dura and pia mater
Has a microscopic appearance of spider web
Contains arachnoid granulations that allow CSF to re-enter circulation
Pia mater
Located underneath the sub-arachnoid space
Tightly adhered to the surface of the brain and spinal cord
The dura mater is the outermost layer of the meninges.
Composed of dense, fibrous tissues
Contains periosteal layer and meningeal layer
Dural venous sinuses located between the two layers
Dural reflections or dural folds help hold the brain in place within the skull.
Falx cerebri is the largest dural fold, lies in the longitudinal fissure.
Tentorium cerebelli is oriented horizontally between the cerebrum and cerebellum.
The arachnoid mater is located between the dura and pia mater.
Has a microscopic appearance of spider web
Contains arachnoid granulations that allow CSF to re-enter circulation.
The pia mater is located underneath the sub-arachnoid space.
Tightly adhered to the surface of the brain and spinal cord
The only covering to follow the contours of the brain (the gyri and fissures)
The subarachnoid space is located between the arachnoid and pia mater.
Occupied by thin, connective tissue trabeculae
Contains cerebrospinal fluid (CSF)
The arachnoid granulations allow CSF to re-enter circulation via the dural venous sinuses.
The pia mater is tightly adhered to the surface of the brain and spinal cord.
Cerebrospinal fluid (CSF) is a colorless fluid that circulates within the ventricles, central canal of the spinal cord, and subarachnoid space.
Acts as a cushion for the brain and spinal cord
Formed in the ventricles from the capillaries of the choroid plexus
CSF is absorbed from the subarachnoid space into the venous blood by the arachnoid villi and arachnoid granulations.
Functions of CSF include supporting brain growth, protecting against external trauma, removing metabolites, and transporting biological substances.
Lumbar puncture is a clinical application for CSF analysis.
Hydrocephalus is a pathological accumulation of CSF within brain spaces.
The brain is supplied with blood by the internal carotid artery and vertebral artery.
The anterior cerebral artery supplies the medial and superolateral surfaces of the cerebral hemisphere.
The middle cerebral artery supplies the entire lateral surface of the cerebral hemisphere except along the superolateral margin and occipital pole.
The posterior cerebral artery supplies the inferior portion of the temporal lobe and occipital lobe.
The meninges are protective coverings of the central nervous system.
The dura mater is the dense outermost fibrous covering of the brain.
The dura mater has two layers: outer endosteal and inner meningeal.
The dural reflections or dural folds include falx cerebri, falx cerebelli, tentorium cerebelli, and diaphragma sella.
The dural venous sinuses are located between the two layers of the dura mater.
The superior sagittal sinus is located at the attached border of the superior sagittal sinus.
Terminates into transverse sinus
Communicates with foramen cecum with the veins of the frontal air sinus & veins of the nose
Inferior Saggital Sinus
Located at the posterior free border of falx cerebri
Joins the great cerebral vein of Galen to form the straight sinus
Straight Sinus
Usually opens into the left transverse sinus
Transverse Sinus
Paired sinus & the widest, begins at the internal occipital protuberance
Lies in the transverse groove of the skull & attached to the margin of the tentorium cerebelli
Terminates by becoming sigmoid sinus
Tributaries of transverse sinus:
Veins from cerebrum & cerebellum
Occipital diploic vein
Superior petrosal sinus
Superior sagittal sinus
Straight sinus
Superior Petrosal Sinus
Very narrow sinus which begins in the posterior end of cavernous sinus
Runs along the upper border of petrous temporal bone
Attached to the margin of tentorium
Ends in the transverse sinus at the point where it continuous with sigmoid sinus
Cavernous Sinus
Short wide channel that lies on the side of the body of sphenoid, extending from medial end of superior orbital fissure to apex of the petrous temporal bone
Tributaries:
Anterior: receives ophthalmic veins & spheno-parietal sinus
Posterior: receives one or more cerebral veins and a large superficial middle cerebral vein
Inferior: communicates with venous plexuses outside the skull through emissary veins
Structures traversing the cavernous sinus:
Cranial Nerves III, IV, VI
Ophthalmic & maxillary divisions of trigeminal nerve
Internal carotid artery
Cranial Arachnoid
Forms a fold between the cerebellum & medulla
At base of brain, enshrouds the olfactory bulbs & tracts, while outer surface stretches as continuous sheet from one temporal lobe to another
The sheet serves as a bridge over interpeduncular fossa & stems of lateral fissure
Space in between arachnoid & pia is called subarachnoid space
Cisterns:
Cisterna basalis:
Lies between the cerebrum divided by optic chiasm into two parts
Cisterna chiasmatis
Cisterna interpeduncularis
Cisterna magna:
Lies between splenium of corpus callosum & superior surfaces of the cerebellum & mesencephalon
Cranial Pia Mater:
Closely applied on the external surface of the brain dipping in all fissures & sulci
Inner surface receives numerous attachments from processes of neuroglia resulting in pia-glial membrane
Sends strong vascular duplication into great transverse fissures of the encephalon
Transverse cerebellar fissure: between the cerebellum & medulla
Transverse cerebral fissure: between cerebellum, mesencephalon, diencephalon & overhanging cerebral hemispheres
Duplications spread over the 3rd & 4th ventricles and known as choroid plexus of these ventricles
CSF Circulation
Emissary Veins: veins that connect the veins outside the skull with dural venous sinuses
Parietal emissary vein
Emissary vein that passes through the foramen cecum
Mastoid emissary vein
Posterior condylar emissary vein
Emissary vein that passes the carotid canal
Ophthalmic vein
Cranial Nerves:
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Acoustic
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Classification of CN:
Purely sensory: afferent fibers, carry impulses towards the brain (CN I, II, VIII)
Purely motor: efferent fibers, carry impulses away from brain (CN III, IV, VI, XI, XII)
Mixed: both sensory & motor fibers (CN V, VII, IX, X)
Summary of Cranial Nerves and their functions
Summary of Cranial Nerves and their functions (continued)
Spinal Nerves & Autonomics
Spinal Nerve:
Union of dorsal roots and ventral roots of the spinal cord
Mixed nerves containing axons of both sensory and somatic motor neurons
31 Nerves connecting the spinal cord and various body regions
Plexuses:
Cervical plexus: originate from C1 to C4, innervate muscles attached to hyoid bone
Brachial plexus: from C5 to T1, supplies upper limb and shoulder
5 major nerves derived from brachial plexus:
Musculocutaneous nerve
Axillary nerve
Radial nerve
Median nerve
Ulnar nerve
Lumbosacral plexus: from T12-L5, supply the lower limb
Branches:
Obturator nerve
Femoral nerve
Ischiatic or sciatic or tibial nerve
Common fibular nerve
Lumbosacral plexus (continued)
Branches:
Obturator nerve
Femoral nerve
Tibial nerve
Common Fibular nerve:
Innervates lateral thigh and leg and some intrinsic muscles of the foot.
Sciatic nerve:
Tibial and common fibular nerves are bounded by connective sheath, forming the sciatic nerve.
Autonomic Nervous System:
Parasympathetic Division:
Preganglionic neurons come from the brain or sacral region of the spinal cord.
Synapse on ganglia located near or in effector organs.
Sympathetic Division:
Thoraco-lumbar region.
General Senses:
Light touch, pressure, touch, pain, temperature, awareness of limb position and motion.
Receptors:
Specialized cells that recognize general senses.
Part of neurons that send signals.
Five functional types of receptors:
Mechanoreceptors: Mechanical deformation.
Thermoreceptors: Temperature changes.
Nociceptors: Stimuli that cause damage to tissues.
Electromagnetic receptors: Changes in light intensity and wavelength.
Chemoreceptors: Chemical changes associated with taste, smell, O2 and CO2 concentration in the blood.
Classification of receptors according to origin or location of stimulus:
Exteroceptors: Stimuli from outside the body.
Interoceptors/Visceroceptors: Stimuli arising within the body.
Proprioceptors: Respond to muscle or tendon stretch and help monitor body position.
Types of receptors according to structure:
Non-encapsulated: Free nerve endings, Merkel's tactile receptors, hair root plexus.
Encapsulated: Meissner's corpuscles, Pacinian corpuscles, Kraus end-bulb receptor, Ruffini's receptors, muscle spindles.
Meissner's corpuscles:
Location: Papillary of the dermis, may be present in skin of nipples and genitalia.
Ovoid shape, consist of Schwann cells arranged transversely across the long axis of corpuscle.
Very sensitive to touch and rapidly adapting mechanoreceptors.
Distinguish two-point structures.
Pacinian Corpuscle:
Pressure and vibration receptors.
Location: Deep dermis, joint capsule, internal organs.
Capsule consists of concentric lamellae of flattened cells.
Golgi mazzoni corpuscles (genital corpuscle) are similar to pacinian corpuscles but smaller in size.
Kraus end bulb:
Cold receptors.
Location: Dermis of the skin, conjunctiva, mucosa of the tongue, external genitalia (glans penis and clitoris).
Golgi tendon organ:
For proprioception.
Muscle Spindles:
For proprioception.
General Sense Pathway:
First order neuron: N1 (Sensory neuron).
Second order neuron: N2 (Association neuron).
Third order neuron: N3 (Motor neuron).
Functional classification of fibers:
Afferent fibers (sensory):
General Somatic Fibers (GSA): Carry exteroceptive and proprioceptive information.
General Visceral Afferent Fibers (GVA): Carry interoceptive information from receptors in visceral structures.
Special Somatic Afferent Fibers (SSA): Convey sensory information from special senses (eye, ear).
Special Visceral Afferent Fibers (SVA): Carry impulses from olfactory and gustatory receptors.
Motor fibers (efferent):
General Somatic Efferent Fibers (GSE): Innervate striated skeletal muscles.
General Visceral Efferent Fibers (GVE): Innervate smooth muscle, cardiac muscles, and regulate glandular secretion.
Special Efferent Fibers: Innervate musculature of branchiomeric origin.
Special Visceral Efferent Fibers (SVE): Innervate striated muscles derived from pharyngeal arches.
Afferent Fibers:
Motor Fibers with cell origin from the spinal cord, brainstem, and autonomic ganglia are referred to as General Efferent Fibers.
Anterolateral system:
Lateral Spinothalamic tract: For pain and temperature except the head region.
Anterior Spinothalamic tract: For crude touch, light touch, and light pressure except the head region.
General Senses:
Includes pain, temperature, touch, pressure, vibration, and proprioception.
Receptors for these sensations are distributed throughout the body.
Specificity:
Allows each receptor to respond to a particular stimulus.
Simplest receptors are free nerve endings.
General Sense Receptors:
Three basic types: Exteroceptors, proprioceptors, interoceptors.
Four specific types: Nociceptors, thermoreceptors, mechanoreceptors, chemoreceptors.
Nociceptors (pain receptors):
Found in superficial portions of the skin, joint capsules, periostea of bone, around walls of blood vessels.
Free nerve endings with large receptive fields.
Thermoreceptors (temperature sensors):
Free nerve endings located in the dermis of the skin, skeletal muscles, liver, hypothalamus.
Cold receptors are more numerous than warm receptors.
No difference between warm or cold receptors structurally
Krause end bulbs detect cold
Ruffini endings detect warmth
Mechanoreceptors are sensitive to stimuli that distort the cell membrane
Three classes of mechanoreceptors: tactile receptors, baroreceptors, and proprioceptors
Tactile receptors provide the sensation of touch, pressure, and vibration
Baroreceptors detect pressure changes in blood vessels and digestive, reproductive, and urinary tracts
Proprioceptors monitor the position of joints
Various types of tactile receptors include free nerve endings, root hair plexus, Merkel discs, Meissner's corpuscles, Pacinian corpuscles, and Ruffini corpuscles
Chemoreceptors can detect small changes in the concentration of specific chemicals or compounds
They respond to water soluble and lipid soluble substances dissolved in surrounding fluid
Chemoreceptors play a major role in the senses of taste and smell
The heart is a hollow muscular organ shaped like an inverted cone
It is located between the lungs in the middle mediastinum
The heart has two closed circuits: the pulmonary circuit and the systemic circuit
The systemic circuit includes arteries, arterioles, capillaries, venules, and veins
The heart is bounded by the sternum anteriorly and vertebrae posteriorly
The pericardium is the connective tissue covering of the heart and base of the great vessels
It has two layers: fibrous pericardium and serous pericardium
The fibrous pericardium is tough and non-elastic, preventing overstretching of the heart
The serous pericardium is a thinner, more delicate membrane with a parietal layer and a visceral layer
The walls of the heart consist of the epicardium, myocardium, and endocardium
The heart has four chambers: right atrium, left atrium, right ventricle, and left ventricle
The chambers are separated by internal structures called septa
The heart has valves, including atrioventricular valves and semilunar valves
The right atrium receives blood from various sources and is divided into a right auricle and a posterior principal cavity or sinus venarum
The wall of the right atrium contains musculi pectinati and a crista terminalis
The left atrium receives blood from the pulmonary veins and has a smooth wall except for the auricular portion
The ventricles are the actual pumps of the heart and have thicker walls than the atria
The fibrous skeleton of the heart provides support and attachment for muscles and valves
Coronary arteries supply blood to the heart, including the left coronary artery and the right coronary artery
Coronary veins drain blood from the heart, including the coronary sinus and its tributaries
The heart has major types of blood vessels: arteries, veins, and capillaries
Arteries have a smaller lumen and thicker walls compared to veins
Arteries stretch and recoil to increase pressure, while veins distend but do not have high-pressure blood flow
Arteries transport oxygenated blood, except for the pulmonary artery, while veins transport deoxygenated blood, except for the pulmonary vein
Capillaries are the smallest blood vessels and are involved in the exchange of nutrients and waste materials between blood and tissue cells
The aorta is the largest artery of the body and has four parts: ascending aorta, arch of the aorta, thoracic/descending aorta, and abdominal aorta
The ascending aorta arises from the left ventricle and gives rise to the right and left coronary arteries
The arch of the aorta continues from the ascending aorta and branches into the brachiocephalic artery, left common carotid artery, and left subclavian artery
Common carotid arteries supply blood to the head and neck, with the right common carotid artery arising from the brachiocephalic artery and the left common carotid artery arising from the arch of the aorta
Subclavian arteries supply blood to the upper extremities
Various arteries supply blood to different parts of the body, including the axillary artery, brachial artery, radial artery, and ulnar artery
Thoracic or descending aorta
Begins from the end of the arch of the aorta at the level of T4
Descends to the diaphragm to become abdominal aorta
Abdominal or ascending aorta
Continuation of the thoracic portion
Passes through the diaphragmatic opening at the level of T12 into the abdominal cavity
Branches of thoracic aorta
Visceral branches
Bronchial, esophageal, pericardial & mediastinal arteries
Parietal branches
Posterior intercostal, subcostal & superior phrenic arteries
Branches of abdominal aorta
Visceral
Paired: middle suprarenal, renal & testicular or ovarian
Single: coeliac, superior mesenteric, inferior mesenteric
Parietal
Paired: inf. Phrenic, lumbar & common iliac
Single: median sacral
Terminal branches
Right & left common iliac arteries
Median sacral arteries
Divisions:
Internal iliac / hypogastric – supplies pelvic organs
External iliac – continues as femoral artery
Blood Supply of the Brain
Main sources:
Internal carotid artery
Vertebral artery
Blood Supply of the Lower Extremities
The common iliac artery at the level of the sacroiliac joint divides into:
Internal iliac artery
External iliac artery
Internal iliac artery supplies the pelvic organs
External iliac artery continues in the thigh as femoral artery, then at the back of the knee becomes popliteal artery, which divides into anterior & posterior tibial arteries
Major Veins of Systemic Circulation
Superior vena cava
Drains deoxygenated blood from the head, neck, upper limb & thorax into the right atrium
Inferior vena cava
Drains deoxygenated blood from the lower parts of the body into the right atrium
Azygous System
Located on either side of the vertebral column
Drains the viscera within the mediastinum, as well as the back and thoracoabdominal walls
Consists of the azygos vein and its two main tributaries: the hemiazygos vein and the accessory hemiazygos vein
Azygous vein
Formed by the union of right ascending lumbar & right subcostal vein
Passes the diaphragm and opens into the back of SVC
Hemizygous vein
Formed by the union of left ascending lumbar & left subcostal vein
Opens into azygous vein at T7 level
Join the SVC & IVC
Responsible for draining the thoracic wall and upper lumbar region
Provides important collateral circulation between the superior and inferior venae cavae should they become obstructed
Portal Circulation
A system of blood vessels that begins and ends in capillaries
Connecting veins between arterial and venous circulation
Veins between the connected capillaries are called portal veins
Blood draining from the capillary bed of one structure flows through larger vessels to supply the capillary bed of another structure, before returning to the heart
Hepatic portal carries nutrients from digestion to the liver to store and metabolize, after a meal
Blood from the intestines goes through portal circulation to the liver
From intestinal veins, it goes through superior mesenteric veins, joins splenic vein, then portal vein, and finally reaches the liver
Cardiovascular system
Composed of:
A. heart
B. blood vessels
Heart
Main pumping organ and propels blood to different areas of the body
Location: middle mediastinum, between the lungs and on its posterior boundary is the vertebral column
Size: as big as the fist
Generates blood pressure
Contraction generates blood pressure required for blood flow through blood vessels
Routes blood
The heart separates the pulmonary & systemic circulations to ensure the flow of oxygenated blood to tissues
Ensures one-way blood flow
The valves of the heart ensure one-way flow of blood through the heart to the blood vessels
Regulates blood supply
Changes in heart rate and force of heart contraction match blood flow to changing metabolic needs of the tissues during rest, exercise, and changes in body position
Cone shape, apex directing on the 5th ICS MCL
Base directed posterior, superiorly to the right
Anteriorly lies below the 2nd rib and relatively fixed because of the great blood vessels
Apex is freely movable
Pericardium
A. fibrous pericardium
B. serous pericardium
Fibrous pericardium
Dense inelastic connective tissue
Anchors the heart within the mediastinum
Protects the heart and prevents overstretching
Serous pericardium
Forms double layers
A. parietal layer
Outer layer fused with the fibrous pericardium
B. visceral layer
Inner layer, tightly adhering on the surface of the heart (superior)
Also called epicardium
Pericardial cavity
Space between the parietal & visceral layer
Filled with slippery pericardial fluid to reduce friction during heart movement
Inflammation: pericarditis
External features of the heart
The right & the left atria are located at the base of the heart
The right & left ventricles extend from the base of the heart towards the apex
Blood supply
A. right & left coronary arteries
Direct branch of the aorta
B. coronary sinus
Chambers of the heart
A. atrium
Right and left atrium
B. ventricles
Right & left ventricles
Septa
A. interatrial septum
Between two atrium
B. interventricular septum
Between two ventricles
Heart valves
Called cusps
A. atrioventricular valves
Between atrium and ventricles
A.1. tricuspid valve (RA/RV)
A.2. mitral valve or bicuspid valve (LA/LV)
B. semilunar valves
B.1. pulmonic valve (RV/PT)
B.2. aortic valve (LA/AA)
Features of the right atrium and left atrium
Size: wider (right atrium), narrower (left atrium)
Auricle-ear-like structure outside the atrium: present in bigger size (right atrium), present in smaller size (left atrium)
Pectinate muscles-parallel muscle bundles: found in right atrium auricle & anterior wall of the right atrium, present in left atrium
Fossa ovalis-remnant of fetal foramen ovale (oval depression seen at the septal wall): none (right atrium), present (left atrium)
Openings of blood vessels
Superior vena cava, inferior vena cava, coronary sinus (right atrium)
4 pulmonary veins (left atrium)
Features of the right ventricle and left ventricle
Lumen (space): crescent shape (right ventricle), circular (left ventricle)
Thickness of wall: thin (right ventricle), thicker (left ventricle)
Chorda tendineae-tendon-like chords attached to the cusp valves: present (right ventricle), present (left ventricle)
Papillary muscles-nipple-like attached to chorda tendineae: present (right ventricle), present (left ventricle)
Trabeculae carnae-coarse cardio muscle fiber ridges along the cardiac wall: present (right ventricle), present (left ventricle)
Moderator band-specialized muscle column at the septal wall- it prevents overdistention of right ventricle: present (right ventricle), none (left ventricle)
Pulmonic valve: present (right ventricle), none (left ventricle)
Conduction system of the heart
SA node or the sino-atrial node: pacemaker or site where the rhythm of electrical excitation causes the heart to contract
Atrioventricular node or the AV node: lies at the base of the right atrium near the interatrial septum
Atr
One heartbeat consists of the contraction and relaxation of atria and ventricles
The purpose is to force blood from areas of higher pressure to lower pressure
Systole phase: contraction phase following depolarization
Diastole phase: relaxation phase following repolarization
Elastic arteries: also known as conducting arteries, carry large volumes of blood away from the heart
The walls of elastic arteries are resilient due to a high density of elastic fibers and few smooth muscle cells
Muscular arteries: medium-sized arteries that distribute blood to various organs
Arterioles: smaller branches of arteries that can constrict to control blood flow
Collect blood from all tissues and organs and return it to the heart
Classified according to size: venules, medium-sized veins, and large veins
Medium-sized veins have thin tunica media and few smooth muscle cells
Large veins have all three tunica layers and a thick tunica externa
Arteries carry blood away from the heart, while veins carry blood toward the heart
Arteries have thick walls and carry blood under high pressure, while veins have thin walls and carry blood under low pressure
Arteries have a pulse flow, while veins have a smooth flow
Arteries have a narrow lumen diameter, while veins have a large lumen diameter
Arteries do not have valves, while veins have valves
Arteries carry oxygen-rich blood (except pulmonary artery), while veins carry oxygen-poor blood (except pulmonary veins)
Function: material exchange with tissues
Capillaries have low pressure and extremely narrow lumen diameter
Capillaries have a single tunica intima layer and lack smooth muscle and elastic fibers
Function of the Lymphatic System:
Returns leaked fluids from the blood vascular system back to the blood
Removes foreign material from the lymph stream
Provides a site for immune surveillance
Transports absorbed lipids from meals
Consists of three parts: lymphatic vessels, lymphatic organs, and lymph nodes
Lymph capillaries: blind-ended tubes where the transport system begins, permeable and found in almost all organs except CNS, bone, teeth, and bone marrow
Lymphatic collecting vessels: similar in structure to veins but with thinner walls, collect lymph from lymphatic capillaries
Lymphatic trunks: formed by the union of the largest collecting vessels, drain large areas of the body
Lymphatic ducts: right lymphatic duct and thoracic duct, empty into the internal jugular vein and subclavian vein
Lymphatic system lacks an organ that acts as a pump
Lymphatic system is maintained by the milking action of active skeletal muscles, pressure changes in the thorax, valves to prevent backflow, and pulsation of nearby arteries
Pathogens and cancer cells can spread through the lymphatic capillaries
Similarities:
Lined with a simple squamous endothelium
Have fibrous connective tissue adventitia wrapping their outer surfaces
Transmit fluid in a single direction with little or no backflow permitted
Differences:
Lymph vessels are delicate and thin-walled, lack a tunica media with smooth muscle
Lymph vessels transmit lymph, while blood vessels transmit blood
Lymph vessels have valves, while only some veins and no arteries have valves
Lymph vessels form an open system, while blood vessels form a closed system
Lymph nodes: filter lymph and add antibodies, contain macrophages and play a role in immune response
Thymus gland: important during early years of life, produces immunocompetent cells
Spleen: largest lymphoid organ, involved in lymphocyte proliferation, immune surveillance and response, and blood cleansing
Mucosa Associated Lymphoid Tissues (MALT): tonsils and Peyer's patches
Distributed along lymphatic vessels, filter lymph and add antibodies
Macrophages within lymph nodes engulf and destroy bacteria, cancer cells, and foreign materials
Structure: fibrous capsule, cortex with primary follicles of lymphocytes, medulla with medullary cords and sinuses
Found in the neck and thorax, prominent in newborns and atrophies after puberty
Continues to produce immunocompetent cells even after atrophy
Soft, blood-rich organ located in the abdomen
Functions: lymphocyte proliferation, immune surveillance and response, blood cleansing
Structure: surrounded by a fibrous capsule, contains lymphocytes, macrophages, and erythrocytes
Red pulp and white pulp are two components of the spleen.
Red pulp is where worn-out red blood cells (RBCs) and blood-borne pathogens are destroyed.
Composed of macrophages and erythrocytes.
White pulp is where immune functions take place.
Composed mainly of lymphocytes.
MALT is a set of lymphoid tissues located in mucous membranes of the body.
It helps protect against pathogens entering the body.
Includes:
Tonsils
Peyer's patches
Appendix
Tonsils are a ring of lymphoid tissues around the entrance of the pharynx (Waldeyer's Ring).
Types of tonsils:
Palatine tonsils: Located on either side at the posterior end of the oral cavity.
Pharyngeal tonsil (adenoids): Located on the posterior wall of the nasopharynx.
Lingual tonsil: Located at the base of the tongue.
Tonsils are not fully encapsulated.
They have invaginations forming blind-ended structures called crypts, which trap bacteria and particulate matters.
Peyer's patches are large clusters of lymph nodules found in the ileum.
They consist of macrophages that capture and destroy bacteria, preventing them from reaching the intestinal wall.
The appendix is a tubular offshoot of the first portion of the large intestine.
It contains a high concentration of lymphoid tissues.
The appendix generates many memory lymphocytes for long-term immunity.
Located at the posterior cranial fossa
Functions:
Control balance and posture coordination of skilled voluntary movements
Movement planning
Command to move
Overlies the posterior side of the pons & medulla
Shallow anterior cerebellar incisure superiorly
Deeper incisure inferiorly
Superficial layer: gray matter
Inner layer: white matter called the arbor vitae
Symmetrical hemispheres connected by vermis
Furrows called fissures: anterior and posterolateral
Longitudinal Division:
Lateral zone
Intermediate zone
Vermis
Nuclei:
Fastigeal nucleus: most medial; contains small & large multipolar neurons
Globose nucleus: contains small & large multipolar neurons
Emboliform nucleus: wedge-shaped mass composed of large multiform nucleus with dendrites
Dentate nucleus: largest & most lateral; appears as convoluted mass resembling the olivary nucleus
Lobes:
Anterior lobe: control posture, locomotion & fine motor coordination
Posterior lobe: control posture, locomotion & fine motor coordination
Flocculonodular lobe: control balance & eye movement
Fissures:
Primary fissure
Posterolateral fissure
Horizontal fissure
Archicerebellum: oldest; regulation of equilibrium and posture; receives input from the vestibular nerve and medial vestibular nuclei
Paleocerebellum: associated with proprioceptive & exteroceptive inputs from head and body; regulates muscle tone
Neocerebellum: largest and newest; associated with neocortex of cerebrum, pontine nuclei, & inferior olivary nucleus of medulla; muscle coordination of phasic movements
Superior cerebellar peduncle (Brachium conjunctivum): connects cerebellum to midbrain; forms the largest cerebellar efferent bundle; fibers arise from dentate, emboliform & globose nuclei
Middle cerebellar peduncle (brachium pontis): connects cerebellum to pons; fibers arise from pons thru ponto-cerebellar tract; consist of afferent fibers
Inferior cerebellar peduncle (brachium restiformins): connects the cerebellum with the medulla; conveys unconscious proprioceptive & exteroceptive information to the cerebellum
Cerebellum found below the occipital lobe of the cerebrum & behind the medulla & pons of the brain stem & within the posterior cranial fossa
Separated from these lobes by the tentorium cerebelli, a tough layer of dura mater
50% of the total number of neurons in the brain
Considered a motor structure, because cerebellar damage leads to impairments in motor control & posture
Cerebellum modifies the motor commands of the descending pathways to make movements more adaptive & accurate
Maintenance of balance & posture
Coordination of voluntary movements
Motor learning
Cognitive functions such as language
Ventricles are a communicating network of cavities
Choroid plexus produces cerebrospinal fluid (CSF)
Ventricles are lined with specialized connective tissue called ependyma
Ventricles are connected by tight junctions forming the blood-CSF barrier
Lateral ventricle: found inside the cerebral hemispheres; divided into central portion and lateral extensions or horns
Third ventricle: small, slit-like cavity in the center of the diencephalon between the two thalami; continuous with the cerebral aqueduct of Sylvius
Fourth ventricle: diamond-shaped cavity located between the pons and the cerebellum
The meninges are membranous coverings of the brain and spinal cord.
Layers of the meninges:
Pachymeninx (dura mater)
Composed of dense, fibrous tissues
Contains periosteal layer and meningeal layer
Dural venous sinuses located between the two layers
Leptomeninges
Arachnoid mater
Located between the dura and pia mater
Has a microscopic appearance of spider web
Contains arachnoid granulations that allow CSF to re-enter circulation
Pia mater
Located underneath the sub-arachnoid space
Tightly adhered to the surface of the brain and spinal cord
The dura mater is the outermost layer of the meninges.
Composed of dense, fibrous tissues
Contains periosteal layer and meningeal layer
Dural venous sinuses located between the two layers
Dural reflections or dural folds help hold the brain in place within the skull.
Falx cerebri is the largest dural fold, lies in the longitudinal fissure.
Tentorium cerebelli is oriented horizontally between the cerebrum and cerebellum.
The arachnoid mater is located between the dura and pia mater.
Has a microscopic appearance of spider web
Contains arachnoid granulations that allow CSF to re-enter circulation.
The pia mater is located underneath the sub-arachnoid space.
Tightly adhered to the surface of the brain and spinal cord
The only covering to follow the contours of the brain (the gyri and fissures)
The subarachnoid space is located between the arachnoid and pia mater.
Occupied by thin, connective tissue trabeculae
Contains cerebrospinal fluid (CSF)
The arachnoid granulations allow CSF to re-enter circulation via the dural venous sinuses.
The pia mater is tightly adhered to the surface of the brain and spinal cord.
Cerebrospinal fluid (CSF) is a colorless fluid that circulates within the ventricles, central canal of the spinal cord, and subarachnoid space.
Acts as a cushion for the brain and spinal cord
Formed in the ventricles from the capillaries of the choroid plexus
CSF is absorbed from the subarachnoid space into the venous blood by the arachnoid villi and arachnoid granulations.
Functions of CSF include supporting brain growth, protecting against external trauma, removing metabolites, and transporting biological substances.
Lumbar puncture is a clinical application for CSF analysis.
Hydrocephalus is a pathological accumulation of CSF within brain spaces.
The brain is supplied with blood by the internal carotid artery and vertebral artery.
The anterior cerebral artery supplies the medial and superolateral surfaces of the cerebral hemisphere.
The middle cerebral artery supplies the entire lateral surface of the cerebral hemisphere except along the superolateral margin and occipital pole.
The posterior cerebral artery supplies the inferior portion of the temporal lobe and occipital lobe.
The meninges are protective coverings of the central nervous system.
The dura mater is the dense outermost fibrous covering of the brain.
The dura mater has two layers: outer endosteal and inner meningeal.
The dural reflections or dural folds include falx cerebri, falx cerebelli, tentorium cerebelli, and diaphragma sella.
The dural venous sinuses are located between the two layers of the dura mater.
The superior sagittal sinus is located at the attached border of the superior sagittal sinus.
Terminates into transverse sinus
Communicates with foramen cecum with the veins of the frontal air sinus & veins of the nose
Inferior Saggital Sinus
Located at the posterior free border of falx cerebri
Joins the great cerebral vein of Galen to form the straight sinus
Straight Sinus
Usually opens into the left transverse sinus
Transverse Sinus
Paired sinus & the widest, begins at the internal occipital protuberance
Lies in the transverse groove of the skull & attached to the margin of the tentorium cerebelli
Terminates by becoming sigmoid sinus
Tributaries of transverse sinus:
Veins from cerebrum & cerebellum
Occipital diploic vein
Superior petrosal sinus
Superior sagittal sinus
Straight sinus
Superior Petrosal Sinus
Very narrow sinus which begins in the posterior end of cavernous sinus
Runs along the upper border of petrous temporal bone
Attached to the margin of tentorium
Ends in the transverse sinus at the point where it continuous with sigmoid sinus
Cavernous Sinus
Short wide channel that lies on the side of the body of sphenoid, extending from medial end of superior orbital fissure to apex of the petrous temporal bone
Tributaries:
Anterior: receives ophthalmic veins & spheno-parietal sinus
Posterior: receives one or more cerebral veins and a large superficial middle cerebral vein
Inferior: communicates with venous plexuses outside the skull through emissary veins
Structures traversing the cavernous sinus:
Cranial Nerves III, IV, VI
Ophthalmic & maxillary divisions of trigeminal nerve
Internal carotid artery
Cranial Arachnoid
Forms a fold between the cerebellum & medulla
At base of brain, enshrouds the olfactory bulbs & tracts, while outer surface stretches as continuous sheet from one temporal lobe to another
The sheet serves as a bridge over interpeduncular fossa & stems of lateral fissure
Space in between arachnoid & pia is called subarachnoid space
Cisterns:
Cisterna basalis:
Lies between the cerebrum divided by optic chiasm into two parts
Cisterna chiasmatis
Cisterna interpeduncularis
Cisterna magna:
Lies between splenium of corpus callosum & superior surfaces of the cerebellum & mesencephalon
Cranial Pia Mater:
Closely applied on the external surface of the brain dipping in all fissures & sulci
Inner surface receives numerous attachments from processes of neuroglia resulting in pia-glial membrane
Sends strong vascular duplication into great transverse fissures of the encephalon
Transverse cerebellar fissure: between the cerebellum & medulla
Transverse cerebral fissure: between cerebellum, mesencephalon, diencephalon & overhanging cerebral hemispheres
Duplications spread over the 3rd & 4th ventricles and known as choroid plexus of these ventricles
CSF Circulation
Emissary Veins: veins that connect the veins outside the skull with dural venous sinuses
Parietal emissary vein
Emissary vein that passes through the foramen cecum
Mastoid emissary vein
Posterior condylar emissary vein
Emissary vein that passes the carotid canal
Ophthalmic vein
Cranial Nerves:
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Acoustic
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Classification of CN:
Purely sensory: afferent fibers, carry impulses towards the brain (CN I, II, VIII)
Purely motor: efferent fibers, carry impulses away from brain (CN III, IV, VI, XI, XII)
Mixed: both sensory & motor fibers (CN V, VII, IX, X)
Summary of Cranial Nerves and their functions
Summary of Cranial Nerves and their functions (continued)
Spinal Nerves & Autonomics
Spinal Nerve:
Union of dorsal roots and ventral roots of the spinal cord
Mixed nerves containing axons of both sensory and somatic motor neurons
31 Nerves connecting the spinal cord and various body regions
Plexuses:
Cervical plexus: originate from C1 to C4, innervate muscles attached to hyoid bone
Brachial plexus: from C5 to T1, supplies upper limb and shoulder
5 major nerves derived from brachial plexus:
Musculocutaneous nerve
Axillary nerve
Radial nerve
Median nerve
Ulnar nerve
Lumbosacral plexus: from T12-L5, supply the lower limb
Branches:
Obturator nerve
Femoral nerve
Ischiatic or sciatic or tibial nerve
Common fibular nerve
Lumbosacral plexus (continued)
Branches:
Obturator nerve
Femoral nerve
Tibial nerve
Common Fibular nerve:
Innervates lateral thigh and leg and some intrinsic muscles of the foot.
Sciatic nerve:
Tibial and common fibular nerves are bounded by connective sheath, forming the sciatic nerve.
Autonomic Nervous System:
Parasympathetic Division:
Preganglionic neurons come from the brain or sacral region of the spinal cord.
Synapse on ganglia located near or in effector organs.
Sympathetic Division:
Thoraco-lumbar region.
General Senses:
Light touch, pressure, touch, pain, temperature, awareness of limb position and motion.
Receptors:
Specialized cells that recognize general senses.
Part of neurons that send signals.
Five functional types of receptors:
Mechanoreceptors: Mechanical deformation.
Thermoreceptors: Temperature changes.
Nociceptors: Stimuli that cause damage to tissues.
Electromagnetic receptors: Changes in light intensity and wavelength.
Chemoreceptors: Chemical changes associated with taste, smell, O2 and CO2 concentration in the blood.
Classification of receptors according to origin or location of stimulus:
Exteroceptors: Stimuli from outside the body.
Interoceptors/Visceroceptors: Stimuli arising within the body.
Proprioceptors: Respond to muscle or tendon stretch and help monitor body position.
Types of receptors according to structure:
Non-encapsulated: Free nerve endings, Merkel's tactile receptors, hair root plexus.
Encapsulated: Meissner's corpuscles, Pacinian corpuscles, Kraus end-bulb receptor, Ruffini's receptors, muscle spindles.
Meissner's corpuscles:
Location: Papillary of the dermis, may be present in skin of nipples and genitalia.
Ovoid shape, consist of Schwann cells arranged transversely across the long axis of corpuscle.
Very sensitive to touch and rapidly adapting mechanoreceptors.
Distinguish two-point structures.
Pacinian Corpuscle:
Pressure and vibration receptors.
Location: Deep dermis, joint capsule, internal organs.
Capsule consists of concentric lamellae of flattened cells.
Golgi mazzoni corpuscles (genital corpuscle) are similar to pacinian corpuscles but smaller in size.
Kraus end bulb:
Cold receptors.
Location: Dermis of the skin, conjunctiva, mucosa of the tongue, external genitalia (glans penis and clitoris).
Golgi tendon organ:
For proprioception.
Muscle Spindles:
For proprioception.
General Sense Pathway:
First order neuron: N1 (Sensory neuron).
Second order neuron: N2 (Association neuron).
Third order neuron: N3 (Motor neuron).
Functional classification of fibers:
Afferent fibers (sensory):
General Somatic Fibers (GSA): Carry exteroceptive and proprioceptive information.
General Visceral Afferent Fibers (GVA): Carry interoceptive information from receptors in visceral structures.
Special Somatic Afferent Fibers (SSA): Convey sensory information from special senses (eye, ear).
Special Visceral Afferent Fibers (SVA): Carry impulses from olfactory and gustatory receptors.
Motor fibers (efferent):
General Somatic Efferent Fibers (GSE): Innervate striated skeletal muscles.
General Visceral Efferent Fibers (GVE): Innervate smooth muscle, cardiac muscles, and regulate glandular secretion.
Special Efferent Fibers: Innervate musculature of branchiomeric origin.
Special Visceral Efferent Fibers (SVE): Innervate striated muscles derived from pharyngeal arches.
Afferent Fibers:
Motor Fibers with cell origin from the spinal cord, brainstem, and autonomic ganglia are referred to as General Efferent Fibers.
Anterolateral system:
Lateral Spinothalamic tract: For pain and temperature except the head region.
Anterior Spinothalamic tract: For crude touch, light touch, and light pressure except the head region.
General Senses:
Includes pain, temperature, touch, pressure, vibration, and proprioception.
Receptors for these sensations are distributed throughout the body.
Specificity:
Allows each receptor to respond to a particular stimulus.
Simplest receptors are free nerve endings.
General Sense Receptors:
Three basic types: Exteroceptors, proprioceptors, interoceptors.
Four specific types: Nociceptors, thermoreceptors, mechanoreceptors, chemoreceptors.
Nociceptors (pain receptors):
Found in superficial portions of the skin, joint capsules, periostea of bone, around walls of blood vessels.
Free nerve endings with large receptive fields.
Thermoreceptors (temperature sensors):
Free nerve endings located in the dermis of the skin, skeletal muscles, liver, hypothalamus.
Cold receptors are more numerous than warm receptors.
No difference between warm or cold receptors structurally
Krause end bulbs detect cold
Ruffini endings detect warmth
Mechanoreceptors are sensitive to stimuli that distort the cell membrane
Three classes of mechanoreceptors: tactile receptors, baroreceptors, and proprioceptors
Tactile receptors provide the sensation of touch, pressure, and vibration
Baroreceptors detect pressure changes in blood vessels and digestive, reproductive, and urinary tracts
Proprioceptors monitor the position of joints
Various types of tactile receptors include free nerve endings, root hair plexus, Merkel discs, Meissner's corpuscles, Pacinian corpuscles, and Ruffini corpuscles
Chemoreceptors can detect small changes in the concentration of specific chemicals or compounds
They respond to water soluble and lipid soluble substances dissolved in surrounding fluid
Chemoreceptors play a major role in the senses of taste and smell
The heart is a hollow muscular organ shaped like an inverted cone
It is located between the lungs in the middle mediastinum
The heart has two closed circuits: the pulmonary circuit and the systemic circuit
The systemic circuit includes arteries, arterioles, capillaries, venules, and veins
The heart is bounded by the sternum anteriorly and vertebrae posteriorly
The pericardium is the connective tissue covering of the heart and base of the great vessels
It has two layers: fibrous pericardium and serous pericardium
The fibrous pericardium is tough and non-elastic, preventing overstretching of the heart
The serous pericardium is a thinner, more delicate membrane with a parietal layer and a visceral layer
The walls of the heart consist of the epicardium, myocardium, and endocardium
The heart has four chambers: right atrium, left atrium, right ventricle, and left ventricle
The chambers are separated by internal structures called septa
The heart has valves, including atrioventricular valves and semilunar valves
The right atrium receives blood from various sources and is divided into a right auricle and a posterior principal cavity or sinus venarum
The wall of the right atrium contains musculi pectinati and a crista terminalis
The left atrium receives blood from the pulmonary veins and has a smooth wall except for the auricular portion
The ventricles are the actual pumps of the heart and have thicker walls than the atria
The fibrous skeleton of the heart provides support and attachment for muscles and valves
Coronary arteries supply blood to the heart, including the left coronary artery and the right coronary artery
Coronary veins drain blood from the heart, including the coronary sinus and its tributaries
The heart has major types of blood vessels: arteries, veins, and capillaries
Arteries have a smaller lumen and thicker walls compared to veins
Arteries stretch and recoil to increase pressure, while veins distend but do not have high-pressure blood flow
Arteries transport oxygenated blood, except for the pulmonary artery, while veins transport deoxygenated blood, except for the pulmonary vein
Capillaries are the smallest blood vessels and are involved in the exchange of nutrients and waste materials between blood and tissue cells
The aorta is the largest artery of the body and has four parts: ascending aorta, arch of the aorta, thoracic/descending aorta, and abdominal aorta
The ascending aorta arises from the left ventricle and gives rise to the right and left coronary arteries
The arch of the aorta continues from the ascending aorta and branches into the brachiocephalic artery, left common carotid artery, and left subclavian artery
Common carotid arteries supply blood to the head and neck, with the right common carotid artery arising from the brachiocephalic artery and the left common carotid artery arising from the arch of the aorta
Subclavian arteries supply blood to the upper extremities
Various arteries supply blood to different parts of the body, including the axillary artery, brachial artery, radial artery, and ulnar artery
Thoracic or descending aorta
Begins from the end of the arch of the aorta at the level of T4
Descends to the diaphragm to become abdominal aorta
Abdominal or ascending aorta
Continuation of the thoracic portion
Passes through the diaphragmatic opening at the level of T12 into the abdominal cavity
Branches of thoracic aorta
Visceral branches
Bronchial, esophageal, pericardial & mediastinal arteries
Parietal branches
Posterior intercostal, subcostal & superior phrenic arteries
Branches of abdominal aorta
Visceral
Paired: middle suprarenal, renal & testicular or ovarian
Single: coeliac, superior mesenteric, inferior mesenteric
Parietal
Paired: inf. Phrenic, lumbar & common iliac
Single: median sacral
Terminal branches
Right & left common iliac arteries
Median sacral arteries
Divisions:
Internal iliac / hypogastric – supplies pelvic organs
External iliac – continues as femoral artery
Blood Supply of the Brain
Main sources:
Internal carotid artery
Vertebral artery
Blood Supply of the Lower Extremities
The common iliac artery at the level of the sacroiliac joint divides into:
Internal iliac artery
External iliac artery
Internal iliac artery supplies the pelvic organs
External iliac artery continues in the thigh as femoral artery, then at the back of the knee becomes popliteal artery, which divides into anterior & posterior tibial arteries
Major Veins of Systemic Circulation
Superior vena cava
Drains deoxygenated blood from the head, neck, upper limb & thorax into the right atrium
Inferior vena cava
Drains deoxygenated blood from the lower parts of the body into the right atrium
Azygous System
Located on either side of the vertebral column
Drains the viscera within the mediastinum, as well as the back and thoracoabdominal walls
Consists of the azygos vein and its two main tributaries: the hemiazygos vein and the accessory hemiazygos vein
Azygous vein
Formed by the union of right ascending lumbar & right subcostal vein
Passes the diaphragm and opens into the back of SVC
Hemizygous vein
Formed by the union of left ascending lumbar & left subcostal vein
Opens into azygous vein at T7 level
Join the SVC & IVC
Responsible for draining the thoracic wall and upper lumbar region
Provides important collateral circulation between the superior and inferior venae cavae should they become obstructed
Portal Circulation
A system of blood vessels that begins and ends in capillaries
Connecting veins between arterial and venous circulation
Veins between the connected capillaries are called portal veins
Blood draining from the capillary bed of one structure flows through larger vessels to supply the capillary bed of another structure, before returning to the heart
Hepatic portal carries nutrients from digestion to the liver to store and metabolize, after a meal
Blood from the intestines goes through portal circulation to the liver
From intestinal veins, it goes through superior mesenteric veins, joins splenic vein, then portal vein, and finally reaches the liver
Cardiovascular system
Composed of:
A. heart
B. blood vessels
Heart
Main pumping organ and propels blood to different areas of the body
Location: middle mediastinum, between the lungs and on its posterior boundary is the vertebral column
Size: as big as the fist
Generates blood pressure
Contraction generates blood pressure required for blood flow through blood vessels
Routes blood
The heart separates the pulmonary & systemic circulations to ensure the flow of oxygenated blood to tissues
Ensures one-way blood flow
The valves of the heart ensure one-way flow of blood through the heart to the blood vessels
Regulates blood supply
Changes in heart rate and force of heart contraction match blood flow to changing metabolic needs of the tissues during rest, exercise, and changes in body position
Cone shape, apex directing on the 5th ICS MCL
Base directed posterior, superiorly to the right
Anteriorly lies below the 2nd rib and relatively fixed because of the great blood vessels
Apex is freely movable
Pericardium
A. fibrous pericardium
B. serous pericardium
Fibrous pericardium
Dense inelastic connective tissue
Anchors the heart within the mediastinum
Protects the heart and prevents overstretching
Serous pericardium
Forms double layers
A. parietal layer
Outer layer fused with the fibrous pericardium
B. visceral layer
Inner layer, tightly adhering on the surface of the heart (superior)
Also called epicardium
Pericardial cavity
Space between the parietal & visceral layer
Filled with slippery pericardial fluid to reduce friction during heart movement
Inflammation: pericarditis
External features of the heart
The right & the left atria are located at the base of the heart
The right & left ventricles extend from the base of the heart towards the apex
Blood supply
A. right & left coronary arteries
Direct branch of the aorta
B. coronary sinus
Chambers of the heart
A. atrium
Right and left atrium
B. ventricles
Right & left ventricles
Septa
A. interatrial septum
Between two atrium
B. interventricular septum
Between two ventricles
Heart valves
Called cusps
A. atrioventricular valves
Between atrium and ventricles
A.1. tricuspid valve (RA/RV)
A.2. mitral valve or bicuspid valve (LA/LV)
B. semilunar valves
B.1. pulmonic valve (RV/PT)
B.2. aortic valve (LA/AA)
Features of the right atrium and left atrium
Size: wider (right atrium), narrower (left atrium)
Auricle-ear-like structure outside the atrium: present in bigger size (right atrium), present in smaller size (left atrium)
Pectinate muscles-parallel muscle bundles: found in right atrium auricle & anterior wall of the right atrium, present in left atrium
Fossa ovalis-remnant of fetal foramen ovale (oval depression seen at the septal wall): none (right atrium), present (left atrium)
Openings of blood vessels
Superior vena cava, inferior vena cava, coronary sinus (right atrium)
4 pulmonary veins (left atrium)
Features of the right ventricle and left ventricle
Lumen (space): crescent shape (right ventricle), circular (left ventricle)
Thickness of wall: thin (right ventricle), thicker (left ventricle)
Chorda tendineae-tendon-like chords attached to the cusp valves: present (right ventricle), present (left ventricle)
Papillary muscles-nipple-like attached to chorda tendineae: present (right ventricle), present (left ventricle)
Trabeculae carnae-coarse cardio muscle fiber ridges along the cardiac wall: present (right ventricle), present (left ventricle)
Moderator band-specialized muscle column at the septal wall- it prevents overdistention of right ventricle: present (right ventricle), none (left ventricle)
Pulmonic valve: present (right ventricle), none (left ventricle)
Conduction system of the heart
SA node or the sino-atrial node: pacemaker or site where the rhythm of electrical excitation causes the heart to contract
Atrioventricular node or the AV node: lies at the base of the right atrium near the interatrial septum
Atr
One heartbeat consists of the contraction and relaxation of atria and ventricles
The purpose is to force blood from areas of higher pressure to lower pressure
Systole phase: contraction phase following depolarization
Diastole phase: relaxation phase following repolarization
Elastic arteries: also known as conducting arteries, carry large volumes of blood away from the heart
The walls of elastic arteries are resilient due to a high density of elastic fibers and few smooth muscle cells
Muscular arteries: medium-sized arteries that distribute blood to various organs
Arterioles: smaller branches of arteries that can constrict to control blood flow
Collect blood from all tissues and organs and return it to the heart
Classified according to size: venules, medium-sized veins, and large veins
Medium-sized veins have thin tunica media and few smooth muscle cells
Large veins have all three tunica layers and a thick tunica externa
Arteries carry blood away from the heart, while veins carry blood toward the heart
Arteries have thick walls and carry blood under high pressure, while veins have thin walls and carry blood under low pressure
Arteries have a pulse flow, while veins have a smooth flow
Arteries have a narrow lumen diameter, while veins have a large lumen diameter
Arteries do not have valves, while veins have valves
Arteries carry oxygen-rich blood (except pulmonary artery), while veins carry oxygen-poor blood (except pulmonary veins)
Function: material exchange with tissues
Capillaries have low pressure and extremely narrow lumen diameter
Capillaries have a single tunica intima layer and lack smooth muscle and elastic fibers
Function of the Lymphatic System:
Returns leaked fluids from the blood vascular system back to the blood
Removes foreign material from the lymph stream
Provides a site for immune surveillance
Transports absorbed lipids from meals
Consists of three parts: lymphatic vessels, lymphatic organs, and lymph nodes
Lymph capillaries: blind-ended tubes where the transport system begins, permeable and found in almost all organs except CNS, bone, teeth, and bone marrow
Lymphatic collecting vessels: similar in structure to veins but with thinner walls, collect lymph from lymphatic capillaries
Lymphatic trunks: formed by the union of the largest collecting vessels, drain large areas of the body
Lymphatic ducts: right lymphatic duct and thoracic duct, empty into the internal jugular vein and subclavian vein
Lymphatic system lacks an organ that acts as a pump
Lymphatic system is maintained by the milking action of active skeletal muscles, pressure changes in the thorax, valves to prevent backflow, and pulsation of nearby arteries
Pathogens and cancer cells can spread through the lymphatic capillaries
Similarities:
Lined with a simple squamous endothelium
Have fibrous connective tissue adventitia wrapping their outer surfaces
Transmit fluid in a single direction with little or no backflow permitted
Differences:
Lymph vessels are delicate and thin-walled, lack a tunica media with smooth muscle
Lymph vessels transmit lymph, while blood vessels transmit blood
Lymph vessels have valves, while only some veins and no arteries have valves
Lymph vessels form an open system, while blood vessels form a closed system
Lymph nodes: filter lymph and add antibodies, contain macrophages and play a role in immune response
Thymus gland: important during early years of life, produces immunocompetent cells
Spleen: largest lymphoid organ, involved in lymphocyte proliferation, immune surveillance and response, and blood cleansing
Mucosa Associated Lymphoid Tissues (MALT): tonsils and Peyer's patches
Distributed along lymphatic vessels, filter lymph and add antibodies
Macrophages within lymph nodes engulf and destroy bacteria, cancer cells, and foreign materials
Structure: fibrous capsule, cortex with primary follicles of lymphocytes, medulla with medullary cords and sinuses
Found in the neck and thorax, prominent in newborns and atrophies after puberty
Continues to produce immunocompetent cells even after atrophy
Soft, blood-rich organ located in the abdomen
Functions: lymphocyte proliferation, immune surveillance and response, blood cleansing
Structure: surrounded by a fibrous capsule, contains lymphocytes, macrophages, and erythrocytes
Red pulp and white pulp are two components of the spleen.
Red pulp is where worn-out red blood cells (RBCs) and blood-borne pathogens are destroyed.
Composed of macrophages and erythrocytes.
White pulp is where immune functions take place.
Composed mainly of lymphocytes.
MALT is a set of lymphoid tissues located in mucous membranes of the body.
It helps protect against pathogens entering the body.
Includes:
Tonsils
Peyer's patches
Appendix
Tonsils are a ring of lymphoid tissues around the entrance of the pharynx (Waldeyer's Ring).
Types of tonsils:
Palatine tonsils: Located on either side at the posterior end of the oral cavity.
Pharyngeal tonsil (adenoids): Located on the posterior wall of the nasopharynx.
Lingual tonsil: Located at the base of the tongue.
Tonsils are not fully encapsulated.
They have invaginations forming blind-ended structures called crypts, which trap bacteria and particulate matters.
Peyer's patches are large clusters of lymph nodules found in the ileum.
They consist of macrophages that capture and destroy bacteria, preventing them from reaching the intestinal wall.
The appendix is a tubular offshoot of the first portion of the large intestine.
It contains a high concentration of lymphoid tissues.
The appendix generates many memory lymphocytes for long-term immunity.