Anatomy Exam 3

What surrounds the heart?

The Heart is surrounded by a lining called the Pericardium

Where is the heart located?

Located in thorax (in middle mediastinum – between lungs)

Which vessels travel out of and into the heart?

Arteries travel out of heart (ascending aorta, pulmonary trunk)

Veins travel into heart (Superior & Inferior vena cava)

What is the purpose of the circulatory system?

To pump blood throughout the body including oxygen, carbon dioxide, nutrients, water, hormone, nitrogenous wastes, etc.

Pathway of blood flow (complete sequence)

Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Artery → Lungs → Pulmonary Vein → Left Atrium → Mitral (bicuspid) Valve → Left Ventricle → Aortic Valve → Aorta

What are the two functional units of the heart?

Pulmonary circuit: right side receives deoxygenated blood and pumps it to lungs

Systemic circuit: left side receives oxygenated blood and pumps it throughout the body

Define artery vs vein

An artery carries blood away from the heart

A vein carries blood towards the heart

What are the four chambers of the heart?

Right Atrium

Left Atrium

Right Ventricle

Left Ventricle

What do pulmonary arteries and veins carry?

Pulmonary arteries – carry deoxygenated blood to lungs

Pulmonary veins – return oxygenated blood to heart

Position of the heart in the thorax

Not a midline structure Situated obliquely: 2/3 left, 1/3 right

Where are the base and apex of the heart located?

Base: at the sternal angle Apex: 5th intercostal space (left), directed anteriorly and left

Borders of the heart

Anterior/inferior border: right and left ventricle

Left/lateral border: left ventricle and left atrium

Right border: right ventricle and right atrium

Superior border: aorta, superior vena cava, pulmonary trunk

What is an auricle?

Each atrium has an Auricle (L: “ear”)

What structures exit the heart from the base?

Pulmonary trunk and Aorta

Coronary sulcus and interventricular sulcus

Coronary sulcus: depression between atria and ventricles

Interventricular sulcus: depression between right and left ventricles

Define pericardium

Peri = around + kardium = heart

A serous membrane that surrounds the heart

Layers of the pericardium

Inner: Visceral pericardium (Epicardium)

Outer: Parietal pericardium

Outside: Fibrous pericardium

What is the pericardial cavity?

A serous fluid-filled space between visceral and parietal pericardium

What is cardiac tamponade?

Accumulation of fluid in pericardial space prevents heart chambers from expanding and filling

Layers of the heart wall

Endocardium: endothelial lining

Myocardium: cardiac muscle

Epicardium: visceral pericardium

Characteristics of cardiac muscle

Striated, branching, single central nuclei

Cells communicate via gap junctions (intercalated discs)

Function of atria vs ventricles

Atria = filling chambers

Ventricles = pumping chambers

Blood flow into atria

Right atrium: receives deoxygenated blood (SVC & IVC)

Left atrium: receives oxygenated blood (pulmonary veins)

Septa of the heart

Interatrial septum: separates atria

Interventricular septum: separates ventricles

Why is left ventricular myocardium thicker?

Because it pumps blood through the aorta to the entire body

Structures of the right atrium

• Sinus venarum (smooth posterior)

• Pectinate muscle (anterior)

• Crista terminalis

• SVC

• IVC

• Coronary sinus

• Fossa ovalis

• SA node

• AV node

Structures of the right ventricle

• Trabeculae carnae

• Conus arteriosus (infundibulum)

• Papillary muscles (anterior, posterior, septal)

• Chordae tendinae

• Moderator band (Purkinje fibers)

Function of papillary muscles and chordae tendinae

Papillary muscles contract to tighten valve cusps

Chordae tendinae connect papillary muscles to valves

Left atrium structure

• Smooth-walled chamber

• Receives four pulmonary veins

• Contains left auricle with pectinate muscle

Left ventricle structure

• Trabeculae carnae

• Thickest myocardium

• Papillary muscles (anterior, posterior)

• Chordae tendinae

Atrioventricular valves

Tricuspid valve (right)

Mitral/Bicuspid valve (left)

Semilunar valves

Aortic semilunar valve

Pulmonary semilunar valve

Fetal circulation – umbilical vessels

Umbilical vein: oxygenated blood to heart

Umbilical artery: deoxygenated blood to placenta

Foramen ovale

Hole allowing blood flow from right atrium to left atrium

Closes after birth → fossa ovalis

Ductus arteriosus

Carries blood from pulmonary artery to aorta

Diverts oxygenated blood away from lungs

Atrial septal defect (ASD)

• Patent foramen ovale remains open

• Right atrium pressure increases over time

• Deoxygenated blood enters left atrium → hypoxia

Ventricular septal defect (VSD)

Incomplete interventricular septum

“Hole in the heart”

Coronary arteries origin and function

• Supply myocardium

• Arise from aorta distal to aortic semilunar valve

• Fill during diastole

Branches of coronary arteries

Left coronary → LAD + circumflex

Right coronary → right marginal + posterior interventricular

What causes myocardial infarction?

Arteriosclerosis → plaque → rupture → thrombus → occlusion → heart attack (cell death)

Cardiac veins and drainage

Great, middle, small cardiac veins

Drain into coronary sinus → right atrium

Smallest cardiac veins

Drain directly into chambers (right atrium and ventricle)

“Running mates” in cardiac circulation

Arteries and veins run together

Great cardiac vein with Anterior Interventricular Artery and Circumflux

Middle cardiac vein with Posterior interventricular artery

Small cardiac artery with Right marginal branch

Cardiac skeleton functions

• Dense connective tissue

• Encircles valves

• Anchors myocardium

• Supports valves

• Blocks electrical impulse between atria and ventricles

Electrical conduction pathway of the heart

SA node → atrial myocardium → AV node → bundle branches → apex → Purkinje fibers → ventricular myocardium

Role of Purkinje fibers

Carry impulses from bundle branches to papillary muscles and ventricular myocardium

Define systole and diastole

Systole = contraction

Diastole = relaxation

Heart sounds (LUB and DUB)

LUB: AV valves close during systole

DUB: semilunar valves close during diastole

Sympathetic and Parasympathetic innervation of the heart

Vagus nerve (CN X) = parasympathetic innervation

Sympathetic nerves innervate cardiac plexus to increase heart rate

Typical pattern of blood flow through vessels

heart → artery → arteriole → capillary → venule → vein → heart

Define systole in terms of vessels and circulation

Systole = ventricular contraction (atrial relaxation), pump blood to lungs, exchange CO2 for O2

Define diastole in terms of vessels and circulation

Diastole = ventricular relaxation (atrial contraction), return O2 to heart

How does the heart move blood through vessels in terms of pressure?

• The pressure in arteries is high

• The pressure in capillaries and veins is low

• Arterioles serve to reduce pressure

• The pressure is high during systole

• The pressure is lower during diastole

What are blood vessels structurally?

Blood vessels are tubules

What are the three tunics of blood vessels?

Tunica intima

Tunica media

Tunica externa

Describe the tunica intima

• Innermost, thinnest layer of an artery or vein

• Smooth endothelial lining

• Supportive basement membrane

What is the internal elastic lamina?

Provides ability to expand and recoil

Separates intima from media

Describe the tunica media

• Smooth muscle under autonomic innervation

• Regulates blood flow and pressure

• Thickest layer in arteries, but thinner in veins

Describe the tunica externa (adventitia)

• Outermost layer

• Made of collagen and elastic fibers

• Supports and protects vessel

• Anchors to surrounding tissues

What is the external elastic lamina?

• Provides ability to expand and recoil

• Separates media from external

• Febestrated

What is the size of a capillary?

A capillary has a diameter of a single Red Blood Cell

How is an artery structured compared to a capillary?

• An artery = a capillary (endothelium + sub-endothelial) with 2 more layers

• Thus 3 tunics around a lumen

Types of capillaries

• Continuous

• Fenestrated

• Sinusoidal

Continuous capillaries

Permeable to gases (O2 & CO2) and water

Fenestrated capillaries

(L. “window”) permeable to molecules and peptides (i.e. hormones)

Sinusoidal capillaries

(“open space”) permeable to proteins and cells Found in liver and spleen

Segments of the aorta

• Ascending aorta

• Arch

• Descending aorta

What happens to the descending aorta after the thorax?

Becomes the abdominal aorta

Branches of the aortic arch

• Brachiocephalic trunk

  • Right Subclavian and Right Common carotid branch off of brachiocephalic trunk

• Left common carotid artery

• Left subclavian artery

Brachiocephalic trunk branches

• Right subclavian artery

• Right common carotid artery

Meaning of “common” in arteries

Indicates an artery that will bifurcate

Abdominal aorta branching

Bifurcates to left and right common iliac arteries

Common iliac artery branches

Internal iliac

External iliac

Subclavian artery pathway in upper limb

• Becomes axillary artery (passes first rib)

• Becomes brachial artery (passes teres major)

Deep brachial artery

• Branch of brachial artery

• Runs posterior to humerus

• Supplies triceps brachii

Brachial artery branches

• Radial artery (lateral)

• Ulnar artery (medial)

Common interosseous artery

• Branch of ulnar artery

• Runs between bones

Palmar arches

• Formed by radial and ulnar arteries

• Anastomose to form collateral circulation of forearm and hand

Collateral circulation around elbow

• Occurs if brachial artery occluded

• Collateral arteries and recurrent arteries anastomose

Define collateral vs recurrent arteries

• Collateral: branches from brachial artery

• Recurrent: branches from radial or ulnar arteries

Common carotid artery branching

Bifurcates to internal and external carotid arteries

External carotid artery function

Supplies external head (lots of branching)

Internal carotid artery function

Supplies anterior and middle cerebral hemispheres

Vertebral artery

Branch of subclavian artery

Supplies posterior cerebral hemisphere

Travels through transverse foramina

Circle of Willis

Cerebral arterial circle providing collateral circulation

Internal carotid artery pathway

Carotid canal → foramen lacerum → middle cranial fossa

Anterior cerebral artery

Supplies frontal lobes

Middle cerebral artery

Supplies anterior portions of parietal and temporal lobes

Vertebral artery pathway

Vertebral artery → Transverse foramina → foramen magnum → posterior cranial fossa → right and left posterior cerebral arteries

Posterior cerebral artery

Supplies posterior parietal, temporal, occipital lobe, cerebellum

Why is the Circle of Willis important?

Provides collateral circulation in case of occlusion

Compensation for internal carotid occlusion

Blood flows via posterior cerebral + posterior communicating and/or anterior cerebral + anterior communicating

Compensation for basilar artery occlusion

Blood flows via middle cerebral + posterior communicating

Lower limb arterial pathway (overview)

Abdominal aorta → common iliac → external iliac → femoral → popliteal → tibial arteries

External iliac artery transition

Passes under inguinal ligament → becomes femoral artery

Deep femoral artery

• Supplies hamstrings

• Runs posterior to femur

Femoral to popliteal transition

Passes through adductor hiatus to posterior knee

Collateral circulation at knee

Genicular arteries connect femoral and tibial arteries

Popliteal artery branches

• Anterior tibial

• Posterior tibial

Posterior tibial artery supply

Posterior compartment (flexor muscles of foot)

• Gastrocnemius

• Soleus

• Plantaris

• Tibialis posterior

• Flexor digitorum longus

• Flexor hallucis longus