Week 11
Circulatory System pdf
The system pumps and directs blood through blood vessels to deliver nutrients and oxygen to tissues and remove wastes from the tissues in the body
consists of:
The Heart: propels blood into the blood vessels
Surrounded by the pericardium, which is a fibrous sac lined by serous mesothelium (simple squamous epi)
Arteries:
Vessels taking blood from the heart and Beyoncé smaller as they branch into the various organs
Carries blood to the tissues
Capillaries:
The smallest vessels
The site of O2, CO2, nutrient and waste product exchange between blood and tissues
Form a complex network of thin, anastomosing tubules called the microvasculature or micro vascular bed
Veins:
Results from the convergence of venues into a system of larger veins which continue enlarging as they approach the heart
Carry blood from tissues to the heart
Pulmonary circulation:
form heart to lungs and back to the heart
Blood gets oxygenated in the lungs, comes back to the heart and is then pumped through the systemic circulation
Blood also gives up carbon dioxide (waste) in lungs and we breathe it out
Systemic Circulation:
blood brings nutrients (and oxygen) to, and removes waste from, tissues
Lymphatic Vascular System:
does not contain blood, instead has lymph
Begins in the interstitium
Has lymphatic capillaries, that are thin walled, closed-ended tubules carrying lymph fluid
They merge to form large vessels and the largest lymph vessels empty into the large veins
They return proteins and fluids from tissues places all over the body to the blood
The internal surface of all components of the heart, blood and lymphatic vessels is lined by a simple squamous epithelium called Endothelium
The Heart:
right and left Atrium (superior chambers) and Ventricles (inferior chambers)
Myocardium = cardiac muscle
Ventricle myocardium is thicker than atrium
Atrioventricular valves (AV)
Between Atria and Ventricle
Flaps (or cusps) of connective tissue anchored in the heart’s fibrous dense irregular connective tissue (Cardiac skeleton)
Attached to the Ventricular Papillary muscles by the Chorda Tendinae
Functions to hold AV valves shut during contractions of ventricle
Prevents valves from exertion into the atria (causes back flow)
Semilunar Valves (SL)
Open up into arteries form each ventricle
Do NOT have Chorda Tendinae
Prevent back flow of blood from arteries into ventricles
Conducting System:
Initiate electrical impulses:
Will cause events that lead to the regular rhythmic heartbeats
Impulses (action potentials) will eventually spread through the atria and ventricular myocardium
Consists of:
Sinoatrial Node (aka. SA Node, pacemaker)
Generates impulses and initiates the conduction, which then goes through the Atrioventricular Node (AV node)
AV node continues into the Bundle of His (AV bundle)
Braches into right and left branches along the intraventricular septum towards apex of the heart
Bundle Branches subdivide further as Purkinje fibers
Extend into myocardium of the ventricles
Rapidly spread the impulses to the ventricular cardiac muscles
Socialized for impulse conduction rather than contraction
Endocardium and Myocardium of ventricles:
The Subendocardial layer of CT in the ventricles surrounds large Purkinje fibers
Purkinje fibers (player staining) contain glycogen but relatively few organelles, and peripheral myofibrils rather than contractile muscle fibers (Myocardium)
Ventricular myocardium:
Much thicker than in atria because it will pump blood with a lot of force into the circulation
Left ventricle is about 3X thicker than the right ventricle because it must produce sufficient force to propel blood through the much larger systemic circulation
Epicardium or Visceral Pericardium:
Epicardium is the visceral layer of the pericardium
Covered by the simple mesothelium which also lines the pericardial space
The mesothelial cells secrete a lubricant fluid (pericardial fluid) that prevents friction within the pericardium
Section of Atrium:
The external tunic of the heart and epicardium
Site of coronary vessels ad contains considerable adipose tissue and other structures
Coronary vessels supply myocardium itch oxygen and nutrients
Valve Leaflet and Cardiac Skeleton:
Section through a Cusp of an atrioventricular valve and attached chorda tendinae
The valve and Chorda tendinae are largely dense irregular connective tissue covered with a thin layer of endothelium
Connective tissue of the cardiac skeleton functions in:
Forming fibrous rings that separate the musculature of the atria from that of the ventricles
Helps coordinate the heartbeat by acting as electrical insulation between atria and ventricles
Conduction o impulses will only go through conducting fibers
Surrounding, anchoring, and supporting all heart valves
Providing firm points of insertion for cardiac muscle in the atria and ventricles
Blood vessels:
all blood vessels EXCEPT capillaries, contain smooth muscle and connective tissue in addition to the endothelial lining
Amount and arrangement of these vascular structures are influenced by mechanical factors, primarily blood pressure, and metabolic factors reflecting the local needs of tissues
Endothelial cells:
Squamous, polygonal, and elongated with the long axis in the direction of blood flow
Act as a semipermeable barrier between the blood and the interstitial tissue fluid
Have smith non-thrombogenic surface on which blood will not clot and secretes agents/factors that:
Control local clot formation
Heparin, tissue plasminogen activator, and von Willebrand factor)
Stimulate smooth muscle contraction
Endothelin-1
Stimulate smooth muscle relaxation
Nitric oxide (NO) and prostacyclin
Smooth muscle cells:
In small arteries and arterioles, they are connected by many more gap junctions and permit vasoconstriction and vasodilation, that are key importance in regulating the overall blood pressure
Connective Tissue
Collagen fibers are found in the subendothelial layer
Elastic fibers (elastin) provide the resiliency required for the vascular all to expand under pressure, especially in large arteries where it forms parallel lamellae
Regularly distributed between the muscle layers
Blood vessel Walls:
Al large to smaller vessels have walls with 3 concentric layers (or tunics) called the intima, media, and adventitious (r externa)
Artery has a thicker Media and relatively narrow lumen
A vein has a larger lumen and its adventitious is the thickest layer
The intima of veins are often folded t form valves
Capillaries have only an endothelium (and a basement membrane or the endothelium) but no other tunics
Large Arteries:
walls of large vessels (arteries and veins) have microvasculature that bring O2 and nutrients to local cells int eh adventitious that are too far from the lumen to be nourished by diffusion from blood I lumen
These are called Vasa Vasorum
Veins carry deoxygenated blood, so they usually have a thin Vasa Vasorum
Elastic arteries:
The aorta, pulmonary artery, and their largest branches
AKA conducting arteries because their major role is to carry blood to smaller arteries
These have very thick tunica media in which elastic lamellae alternate with layers of smooth muscle fibers
During ventricular contractions, elastic layers expands and during ventricular relaxation and pressure drops
These layers recoil and help maintain arterial pressure
Arterial Sensory Structures:
2 separate types of sensory receptors I walls of arteries:
Baroreceptors monitor blood pressure changes re found in 2 places
Carotid sinuses
Send information to brain via the CN IX (Glossopharyngeal nerve”
Aortic Arch
Sends information to the brain through Vagus Nerve (CN X)
Chemoreceptors that monitor blood CO2 and O2 levels, and pH
Found in the carotid and aortic bodies found in walls of carotid sinus and aortic arch
Contain chemoreceptor gloms cells
Muscular Arteries:
as arteries get more distant from the heart, they gradually have relatively less elastin and more smooth muscle in their walls
AKA Distributing arteries
Distribute blood to the organs and help regulate blood pressure by contracting or relaxing the smooth muscle in the media
Arterioles:
smallest arteries branch as arterioles and have one or three smooth muscle layers with NO elastic laminae
Indicate the beginning of an organ’s microvasculature, where exchanges of substances between blood and tissue fluid occur
Capillaries lack media and adventitious tunics
have smallest diameters (4-10 um)
Almost the diameter of a red blood cell
Have slowest blood flow
Arterioles supplying a capillary bed form smaller branches called Metarterioles in which the smooth muscle cells are dispersed as bands that act as precapillary sphincters
Can shunt blood into the venules
The distal portion of the metarteriole, sometimes called a Thoroughfare channel
Lacks smooth muscle cells and merges with the postcapillary venule
Branching from the metarteriole and thoroughfare channel are true capillaries, which lack smooth muscle
Most Capillary beds are supplied by arterioles and drain into venules
Alternatives pathways are found in certain organs
In skin, blood flow can vary according to external temps
Arteriovenous shunts (or anastomoses) temporarily bypass capillaries
In venous portal systems, blood flows through 2 successive capillary beds separated by a portal vein
Delivers substances collected from 1st capillary bed into 2nd bed
I.e. The Hepatic Portal System
In Arterial Portal Systems, capillary beds drain into an artery
Capillaries:
composed of simple layer endothelial cells, rolled up as a tube surrounded by basement membrane
Lumen has blood
Tissues with high metabolic rates (i.e.. Kidneys, liver, cardiac and skeletal muscles) have abundant capillaries
Make up over 90% of the body’s vasculature
have a huge total cross sectional surface area than other vessels
So, they have the slowest, pulsatilla blood flow, which optimizes their function:
allowing the exchange of water and solutes between blood and tissues
Perivascular contractile cells are called Pericytes
Structural variations in capillaries: 3 types
Based on continuity of the endothelial cells and their basement membrane
Continuous Capillaries:
Have tight occluding junctions sealing the intercellular clefts between
All molecules exchanged across the endothelium must cross the cells by diffusion or trans cytosine (across the cell)
Most common
Found in muscle, CT, Lungs, Exocrine glands and nervous tissue
Fenestrated Capillaries:
Have perforations through the endothelial cells allowing greater exchange of substances
Basement membrane is continuous
Found in kidneys, endocrine organs, intestinal walls and choroid plexus
Sinusoids, or Discontinuous Capillaries:
Usually have a wider diameter than the other types
Have discontinuities in endothelial cells and in basement membrane
Found in bone marrow, liver, endocrine glands and spleen
Allow greatest exchange of substances including cells
Venules, Veins and Valves:
Postcapillary venules:
Primary site at which WBC adhere to endothelium and leave the circulation at sites of infection or tissue damage
Veins:
Carry blood back to the heart from microvasculature all over the body
Blood entering veins in under very low pressure and moves toward the heart by contraction of the smooth muscle fibers in the media and by external compressions from surrounding skeletal muscles and other organs
Large Veins:
Big Venous trunks close to the heart
An important feature of the medium and large veins are valves
Consist of thin, paired folds of the tunica intima, projecting across the lumen, rich in elastic fibers and covered on both sides by endothelium
The valves
especially numerous in veins of the legs
Help keep the flow of venous blood directed toward the heart
Lymphatic Capillaries:
collect proteins and excess interstitial fluid from the tissue spaces as lymph fluid and return it to the blood
Lymph is rich in proteins but does not normally contain red blood cells
With exceptions (such as bone marrow and most of the CNS) most tissues with blood microvasculature also contain lymphatic capillaries (AKA Lymphatics)
Lymphatic Vessels:
Lymphatic opening is where proteins and interstitial fluid enters, and opening are help in place by anchoring filaments
Endothelial cells form valves form folds of the intima, preventing back flow of lymph
Larger lymphatic vessels go through structures called Lymph Nodes
Where lymph is processed (filtered) by cells of the immune system
As in veins, lymphatic circulation is aided by external forces with the valves keeping lymph flow unidirectional
Lymphatic vessels ultimately converge as two large trunks
The thoracic duct and the right lymphatic duct
Which empty lymph into blood
Structures of large lymphatic vessels are like those of veins
The lymphatic vascular system also distributes lymphocytes, antibodies, and other immune components That are carried through many organs to and from lymph nodes and other lymphoid tissues
Circulatory System pdf
The system pumps and directs blood through blood vessels to deliver nutrients and oxygen to tissues and remove wastes from the tissues in the body
consists of:
The Heart: propels blood into the blood vessels
Surrounded by the pericardium, which is a fibrous sac lined by serous mesothelium (simple squamous epi)
Arteries:
Vessels taking blood from the heart and Beyoncé smaller as they branch into the various organs
Carries blood to the tissues
Capillaries:
The smallest vessels
The site of O2, CO2, nutrient and waste product exchange between blood and tissues
Form a complex network of thin, anastomosing tubules called the microvasculature or micro vascular bed
Veins:
Results from the convergence of venues into a system of larger veins which continue enlarging as they approach the heart
Carry blood from tissues to the heart
Pulmonary circulation:
form heart to lungs and back to the heart
Blood gets oxygenated in the lungs, comes back to the heart and is then pumped through the systemic circulation
Blood also gives up carbon dioxide (waste) in lungs and we breathe it out
Systemic Circulation:
blood brings nutrients (and oxygen) to, and removes waste from, tissues
Lymphatic Vascular System:
does not contain blood, instead has lymph
Begins in the interstitium
Has lymphatic capillaries, that are thin walled, closed-ended tubules carrying lymph fluid
They merge to form large vessels and the largest lymph vessels empty into the large veins
They return proteins and fluids from tissues places all over the body to the blood
The internal surface of all components of the heart, blood and lymphatic vessels is lined by a simple squamous epithelium called Endothelium
The Heart:
right and left Atrium (superior chambers) and Ventricles (inferior chambers)
Myocardium = cardiac muscle
Ventricle myocardium is thicker than atrium
Atrioventricular valves (AV)
Between Atria and Ventricle
Flaps (or cusps) of connective tissue anchored in the heart’s fibrous dense irregular connective tissue (Cardiac skeleton)
Attached to the Ventricular Papillary muscles by the Chorda Tendinae
Functions to hold AV valves shut during contractions of ventricle
Prevents valves from exertion into the atria (causes back flow)
Semilunar Valves (SL)
Open up into arteries form each ventricle
Do NOT have Chorda Tendinae
Prevent back flow of blood from arteries into ventricles
Conducting System:
Initiate electrical impulses:
Will cause events that lead to the regular rhythmic heartbeats
Impulses (action potentials) will eventually spread through the atria and ventricular myocardium
Consists of:
Sinoatrial Node (aka. SA Node, pacemaker)
Generates impulses and initiates the conduction, which then goes through the Atrioventricular Node (AV node)
AV node continues into the Bundle of His (AV bundle)
Braches into right and left branches along the intraventricular septum towards apex of the heart
Bundle Branches subdivide further as Purkinje fibers
Extend into myocardium of the ventricles
Rapidly spread the impulses to the ventricular cardiac muscles
Socialized for impulse conduction rather than contraction
Endocardium and Myocardium of ventricles:
The Subendocardial layer of CT in the ventricles surrounds large Purkinje fibers
Purkinje fibers (player staining) contain glycogen but relatively few organelles, and peripheral myofibrils rather than contractile muscle fibers (Myocardium)
Ventricular myocardium:
Much thicker than in atria because it will pump blood with a lot of force into the circulation
Left ventricle is about 3X thicker than the right ventricle because it must produce sufficient force to propel blood through the much larger systemic circulation
Epicardium or Visceral Pericardium:
Epicardium is the visceral layer of the pericardium
Covered by the simple mesothelium which also lines the pericardial space
The mesothelial cells secrete a lubricant fluid (pericardial fluid) that prevents friction within the pericardium
Section of Atrium:
The external tunic of the heart and epicardium
Site of coronary vessels ad contains considerable adipose tissue and other structures
Coronary vessels supply myocardium itch oxygen and nutrients
Valve Leaflet and Cardiac Skeleton:
Section through a Cusp of an atrioventricular valve and attached chorda tendinae
The valve and Chorda tendinae are largely dense irregular connective tissue covered with a thin layer of endothelium
Connective tissue of the cardiac skeleton functions in:
Forming fibrous rings that separate the musculature of the atria from that of the ventricles
Helps coordinate the heartbeat by acting as electrical insulation between atria and ventricles
Conduction o impulses will only go through conducting fibers
Surrounding, anchoring, and supporting all heart valves
Providing firm points of insertion for cardiac muscle in the atria and ventricles
Blood vessels:
all blood vessels EXCEPT capillaries, contain smooth muscle and connective tissue in addition to the endothelial lining
Amount and arrangement of these vascular structures are influenced by mechanical factors, primarily blood pressure, and metabolic factors reflecting the local needs of tissues
Endothelial cells:
Squamous, polygonal, and elongated with the long axis in the direction of blood flow
Act as a semipermeable barrier between the blood and the interstitial tissue fluid
Have smith non-thrombogenic surface on which blood will not clot and secretes agents/factors that:
Control local clot formation
Heparin, tissue plasminogen activator, and von Willebrand factor)
Stimulate smooth muscle contraction
Endothelin-1
Stimulate smooth muscle relaxation
Nitric oxide (NO) and prostacyclin
Smooth muscle cells:
In small arteries and arterioles, they are connected by many more gap junctions and permit vasoconstriction and vasodilation, that are key importance in regulating the overall blood pressure
Connective Tissue
Collagen fibers are found in the subendothelial layer
Elastic fibers (elastin) provide the resiliency required for the vascular all to expand under pressure, especially in large arteries where it forms parallel lamellae
Regularly distributed between the muscle layers
Blood vessel Walls:
Al large to smaller vessels have walls with 3 concentric layers (or tunics) called the intima, media, and adventitious (r externa)
Artery has a thicker Media and relatively narrow lumen
A vein has a larger lumen and its adventitious is the thickest layer
The intima of veins are often folded t form valves
Capillaries have only an endothelium (and a basement membrane or the endothelium) but no other tunics
Large Arteries:
walls of large vessels (arteries and veins) have microvasculature that bring O2 and nutrients to local cells int eh adventitious that are too far from the lumen to be nourished by diffusion from blood I lumen
These are called Vasa Vasorum
Veins carry deoxygenated blood, so they usually have a thin Vasa Vasorum
Elastic arteries:
The aorta, pulmonary artery, and their largest branches
AKA conducting arteries because their major role is to carry blood to smaller arteries
These have very thick tunica media in which elastic lamellae alternate with layers of smooth muscle fibers
During ventricular contractions, elastic layers expands and during ventricular relaxation and pressure drops
These layers recoil and help maintain arterial pressure
Arterial Sensory Structures:
2 separate types of sensory receptors I walls of arteries:
Baroreceptors monitor blood pressure changes re found in 2 places
Carotid sinuses
Send information to brain via the CN IX (Glossopharyngeal nerve”
Aortic Arch
Sends information to the brain through Vagus Nerve (CN X)
Chemoreceptors that monitor blood CO2 and O2 levels, and pH
Found in the carotid and aortic bodies found in walls of carotid sinus and aortic arch
Contain chemoreceptor gloms cells
Muscular Arteries:
as arteries get more distant from the heart, they gradually have relatively less elastin and more smooth muscle in their walls
AKA Distributing arteries
Distribute blood to the organs and help regulate blood pressure by contracting or relaxing the smooth muscle in the media
Arterioles:
smallest arteries branch as arterioles and have one or three smooth muscle layers with NO elastic laminae
Indicate the beginning of an organ’s microvasculature, where exchanges of substances between blood and tissue fluid occur
Capillaries lack media and adventitious tunics
have smallest diameters (4-10 um)
Almost the diameter of a red blood cell
Have slowest blood flow
Arterioles supplying a capillary bed form smaller branches called Metarterioles in which the smooth muscle cells are dispersed as bands that act as precapillary sphincters
Can shunt blood into the venules
The distal portion of the metarteriole, sometimes called a Thoroughfare channel
Lacks smooth muscle cells and merges with the postcapillary venule
Branching from the metarteriole and thoroughfare channel are true capillaries, which lack smooth muscle
Most Capillary beds are supplied by arterioles and drain into venules
Alternatives pathways are found in certain organs
In skin, blood flow can vary according to external temps
Arteriovenous shunts (or anastomoses) temporarily bypass capillaries
In venous portal systems, blood flows through 2 successive capillary beds separated by a portal vein
Delivers substances collected from 1st capillary bed into 2nd bed
I.e. The Hepatic Portal System
In Arterial Portal Systems, capillary beds drain into an artery
Capillaries:
composed of simple layer endothelial cells, rolled up as a tube surrounded by basement membrane
Lumen has blood
Tissues with high metabolic rates (i.e.. Kidneys, liver, cardiac and skeletal muscles) have abundant capillaries
Make up over 90% of the body’s vasculature
have a huge total cross sectional surface area than other vessels
So, they have the slowest, pulsatilla blood flow, which optimizes their function:
allowing the exchange of water and solutes between blood and tissues
Perivascular contractile cells are called Pericytes
Structural variations in capillaries: 3 types
Based on continuity of the endothelial cells and their basement membrane
Continuous Capillaries:
Have tight occluding junctions sealing the intercellular clefts between
All molecules exchanged across the endothelium must cross the cells by diffusion or trans cytosine (across the cell)
Most common
Found in muscle, CT, Lungs, Exocrine glands and nervous tissue
Fenestrated Capillaries:
Have perforations through the endothelial cells allowing greater exchange of substances
Basement membrane is continuous
Found in kidneys, endocrine organs, intestinal walls and choroid plexus
Sinusoids, or Discontinuous Capillaries:
Usually have a wider diameter than the other types
Have discontinuities in endothelial cells and in basement membrane
Found in bone marrow, liver, endocrine glands and spleen
Allow greatest exchange of substances including cells
Venules, Veins and Valves:
Postcapillary venules:
Primary site at which WBC adhere to endothelium and leave the circulation at sites of infection or tissue damage
Veins:
Carry blood back to the heart from microvasculature all over the body
Blood entering veins in under very low pressure and moves toward the heart by contraction of the smooth muscle fibers in the media and by external compressions from surrounding skeletal muscles and other organs
Large Veins:
Big Venous trunks close to the heart
An important feature of the medium and large veins are valves
Consist of thin, paired folds of the tunica intima, projecting across the lumen, rich in elastic fibers and covered on both sides by endothelium
The valves
especially numerous in veins of the legs
Help keep the flow of venous blood directed toward the heart
Lymphatic Capillaries:
collect proteins and excess interstitial fluid from the tissue spaces as lymph fluid and return it to the blood
Lymph is rich in proteins but does not normally contain red blood cells
With exceptions (such as bone marrow and most of the CNS) most tissues with blood microvasculature also contain lymphatic capillaries (AKA Lymphatics)
Lymphatic Vessels:
Lymphatic opening is where proteins and interstitial fluid enters, and opening are help in place by anchoring filaments
Endothelial cells form valves form folds of the intima, preventing back flow of lymph
Larger lymphatic vessels go through structures called Lymph Nodes
Where lymph is processed (filtered) by cells of the immune system
As in veins, lymphatic circulation is aided by external forces with the valves keeping lymph flow unidirectional
Lymphatic vessels ultimately converge as two large trunks
The thoracic duct and the right lymphatic duct
Which empty lymph into blood
Structures of large lymphatic vessels are like those of veins
The lymphatic vascular system also distributes lymphocytes, antibodies, and other immune components That are carried through many organs to and from lymph nodes and other lymphoid tissues