CARDIOVASCULAR SYSTEM Flashcards
A muscular tubular organ that pumps oxygenated blood to all parts of the body and receives unoxygenated blood from these body parts
HEART
Consists of four chambers; right and left atria and right and left ventricles
HEART
Supported by the ‘’ “ structures into which cardiac muscle fibers are attached with which the cardiac valves are connected
cardiac skeleton
Innervated by an impulse –
groups of Purkinje fibers that ramify the heart from the anterior vena cava to the ventricular wall and regulate heart contraction.
conducting system -
Innervated by an impulse –
groups of Purkinje fibers that ramify the heart from the anterior vena cava to the ventricular wall and regulate heart contraction.
conducting system -
Cardiac Wall
Composed of three layers, from the outside to the heart lumen:
Epicardium, myocardium and endocardium.
Inner portion of the CT envelope that surrounds the heart.
A thin serous membrane (visceral layer of pericardium that corresponds to the tunica serosa of a tubular organ) overlying the outer surface of the organ.
Epicardium
Epicardium composed of to layers:
- Mesothelium
- Subepicardial layer
A special simple squamous epithelium that covers the epicardium.
Mesothelium
Thin loose connective tissue (mainly reticular fibers) with blood vessels, nerves and adipose cells.
Subepicardial layer
Middle muscular layer of the cardiac wall
Lies internal to the sub epithelial layer of the epicardium.
Myocardium
Thickest layer that corresponds to the t. muscularis of tubular organ.
Composed of a highly vascular ordinary cardiac muscle tissue and Purkinije fibers.
Innermost and thinnest layer of the cardiac wall and forms the cardiac valves.
Corresponds to the t. mucosa of a tubular organ.
Endocardium
The endocardium Composed of three (3) layers:
Subendocardial layer
Subendothelial layer
Endothelium
Layer of loose connective tissue with blood vessels, lymph vessels and occasionally Purkinje fibers, that lies internal to the myocardium.
Subendocardial layer
Thin layer of dense connective tissue with collagen and elastic fibers, blood vessels, Purkinje fibers and adipose cells.
Subendothelial layer
Lining epithelium of special simple squamous epithelium that faces the cardiac lumen.
Endothelium
Folds of endocardium that guard the major orifices of the heart
Cardiac Valves
Guard the left atrioventricular canal.
Bicuspid valves
Guard the right atrioventricular canal.
Tricuspid valves
Guard the ascending aorta and the pulmonary trunk.
Semilunar valves
Made up of dense irregular connective tissue covered by endothelium
Cardiac Valves
Structures that support the cardiac valves and cardiac muscles.
Cardiac Skeleton
Cardiac Skeleton Classified as:
Septum membranaceum, Trigonum fibrosum and Annuli fibrosi.
Fibrous (collagenous) portion of the interventricular septum.
Septum membranaceum
Four fibrous (collagenous) rings that individually surrounds the semilunar valves of the aorta and pulmonary artery and the atrioventricular valves.
Annuli fibrosis
Mass of fibrous (collagenous) tissue located between the atrioventricular canals
Trigonum fibrosum
what animas are the annulum fibrosum of the semilunar valve ossifies to form the os cordis?
Ruminants and older animals:
what animals are annuli fibrosi are nearly cartilagous
Horse and pig
what animal is annuli fibrosi are true hyaline cartilage?
dog
Tubular organs of various diameters that transport blood from and to the heart
Blood Vessels
The wall and lumen vary in thickness and diameter, respectively, depending on the following factors:
The faster the blood velocity or speed, the thicker the wall and the smaller the lumen
The velocity of blood moving through the blood vessels.
The higher the pressure, the thicker the wall and the smaller the lumen of blood vessels.
The pressure with which blood is being propelled.
The higher the volume the thinner the wall and the larger the lumen.
The volume of blood being moved.
Wall consist of one to three layers or tunics depending on the type of blood vessel.
In large vessels the layers from the lumen outward are the
tunica intima, tunica media and tunica adventitia.
Wall consist of one to three layers or tunics depending on the type of blood vessel.
Blood Vessels
Innermost layer that faces the lumen of blood vessel.
Tunica Intima
Tunica Intima Composed of three distinct sublayers, namely:
Endothelium
Subendothelial coat
Elastica interna or internal elastic membrane
A specific type of simple squamous epithelium which lines the blood and lymphatic vessels
Constantly present in all blood and lymph vessels from the largest to the smallest.
Rests on the basal lamina, which separates the endothelium from the next layer.
endothelium
A very thin layer of loose connective tissue underneath the endothelium.
Subendothelial coat
Consist of fibroelastic connective tissue and fibroblast cells.
In the smallest blood vessels, this layer may not be distinctly visible.
A thin condensation of elastic fibers located beneath the subendothelial coat and separates the t. intima from the second layer, the tunica media.
Elastica interna
Wavy appearance because of its elasticity.
The second or middle layer of the wall of blood and lymph vessels.
Tunica media
The Tunica Media Consists of a mixture of :
Smooth muscle fibers arranged in circular pattern around the lumen
Collagenous
Elastic fibers and
Fibroblasts.
Predominate in the t. media of medium size & arteries like the hepatic artery thus medium sized arteries are also called muscular arteries.
Smooth muscle fibers
Predominate in the t. media of large arteries, thus these arteries are also called elastic arteries.
Elastic fibers
In larger blood vessels like the large or elastic artery, the t. media may present tiny blood vessels called v
vasa vasorum
nerve fibers called
nervi vasorum
The outermost and third layer of the blood vessel wall.
Tunica adventitia
the tunica adventitia Consists of the :
External elastic lamina or elastica externa
Dense fibroelastic connective tissue.
Nervi vasorum and vasa vasorum are also present in t. adventitia of large blood vessels.
Three major types of blood vessels:
Arteries
Capillaries
Veins
Arteriovenous anastomosis.
Carry a low volume of blood under high pressure at a high velocity away from the heart to the capillaries.
Present thick walls and relatively small lumens.
The thickest layer of the wall is the tunica media.
Arteries
Arteries classified as:
Elastic or large arteries,
muscular or distributing arteries
Arterioles.
The largest arteries in the body.
Have their own blood supply (vasa vasorum) to nourish the cells
Have their own nerve supply (nervi vasorum) so that the CNS can control blood pressure and initiate contraction of smooth myocytes in the wall when needed.
Conducting or Elastic or Large arteries
Conducting or Elastic or Large arteries
T. intima - typical except that the elastic interna is not distinct because it blends with the t. media.
Conducting or Elastic or Large arteries
T. media — thickest layer.
-Predominantly elastic fibers and few collagen fibers.
-Elastic fibers allow the artery to expand under pressure and recoil to original diameter when the pressure drops again.
-Collagen fibers prevent over-expansion and resist bursting of the vessel.
-Presents vasa vasorum and nervi vasorum.
Conducting or Elastic or Large arteries
T. adventitia - thin; elastica externa is not distinct because it blends with the t. media.
Presents vasa vasorum and nervi vasorum.
Ex. aorta, pulmonary artery
T. adventitia - thin; elastica externa is not distinct because it blends with the t. media.
Presents vasa vasorum and nervi vasorum.
Ex. aorta, pulmonary artery
Branches of the large arteries.
Distribute blood to the different parts of the body.
Usually seen in the company of their counterpart veins and nerve bundles.
Muscular or Distributing arteries
Wall presents an increasing amount of smooth myocytes
and
decreasing amount of elastic fibers
The Muscular or Distributing arteries
Classified as:
Medium and small arteries.
The same wall as the elastic arteries except that the t. media is almost entirely smooth myocytes circularly arranged.
Medium artery
The external and internal elastic laminae are distinct.
In sections, the internal elastic lamina is scalloped.
Ex:
. Brachial, femoral and radial arteries.
The same wall as the medium artery but has smaller diameter.
Found in tissue and organs in the company of small veins and nerve bundles (VAN).
Small artery
Very small arteries with special construction, having relatively narrow lumens and relatively thick walls.
Smooth muscle tonus in their walls regulates the degree of blood pressure within the arterial system.
Arterioles
ARTERIOLES Classified as:
large arteriole
small arteriole
precapillary arteriole
metarteriole
Direct continuation of small artery. It is similar in structure to the small artery except that it has a smaller diameter.
Gives off branches, the small arterioles.
Large arteriole
Similar in structure to large arteriole except that it has a smaller lumen and thinner wall.
Elastica interna — very thin.
T media - 2-3 layers of smooth myocytes.
T. adventilia - predominantly collagen fibers.
Continues as precapillary or terminal arteriole.
Small arteriole
Much smaller than the small arteriole.
Lumen diameter is about the size of an RBC, thus like the capillary, it can only accommodate one RBC at a time.
NO elastic interna
T media - one layer of smooth myocyte
T. adventitia - thin; very little amount of connective tissue.
Continues as the metarteriole.
Precapiliary or terminal arteriole
The smallest arteriole.
Connects with the capillary at one end and the terminal arteriole at the other end.
Similar in structure to the terminal arteriole except that the layer of smooth myocytes in its t. media is replaced by a layer of perivascular Rouget cells
Metarteriole
The smallest and the most numerous type of blood vessels.
Site of exchange of nutrients and waste products of metabolism as well as of oxygen and carbon dioxide between the vascular bed and the surrounding tissues.
The smallest and the most numerous type of blood vessels.
Site of exchange of nutrients and waste products of metabolism as well as of oxygen and carbon dioxide between the vascular bed and the surrounding tissues.
Capillaries
Carry large volume of blood under appreciably diminished pressure and velocity
Very thin wall only endothelium resting on a basal lamina.
Lumen diameter is so small it can only accommodate one RBC at a time.
Capillaries
Classified morphologically as
Continuous capillary,
Fenestrated or perforated capillary,
Porous capillary,
Sinusoidal capillary,
Sinusoid
Sinus.
Capillaries
Endothelial cells that are held together by tight junctions and do not possess interruptions in their cell membrane.
Can move material in and out using a process of sequential endocytosis and exocytosis, as well as simple diffusion for small molecules.
Closed or continuous capillaries
Capillaries
Closed or continuous capillaries
Found in areas where rapid “bulk” transfer of materials between the blood and the tissue is not needed, such as in muscles
Found in adipose tissue, muscle tissue, lung and nervous tissue
Capillaries
Endothelial cells that present pores in the cell membrane.
Pores are 60 to 80 run in diameter and closed by a one layered diaphragm.
Occurs in the endocrine glands and intestinal villi.
Fenestrated or Perforated capillaries
Capillaries
Variation of fenestrated capillaries.
Structurally similar to the fenestrated capillaries except that the pores are patent (not covered by diaphragm).
Found in areas where immediate movement of materials is a functional necessity.
Constitute the renal glomeruli.
Porous capillaries
Capillaries
Endothelial cells possess interruptions in their cell membrane.
Discontinuous capillaries
Discontinuous capillaries found which orgnas
Found in liver, bone marrow and spleen.
CAPILLARIES
Very large, irregularly shaped capillaries.
Lined by non-phagocytic endothelial cells.
Sinusoidal capillaries
Sinusoidal capillaries present which organs?
Present in endocrine glands and carotid/aortic bodies.
Large, irregular capillary-type vessel.
Similar in structure to, but larger than sinusoidal capillaries.
Endothelial cells are both phagocytic (littoral cells or macrophages) and nonphagocytic
Sinusoids
Sinusoids which organ are present
Bone marrow and liver
Capillaries
Larger than sinusoids.
Lined by nonphagocytic endothelial cells that rest on a discontinuous basal lamina.
Sinuses
Sinuses Present in
Where they occur as spaces between medullary cords and may contain either blood or lymph.
Lymph nodes, hemolymph nodes and hemal nodes
Vessels that return blood from the tissues to the heart.
Carry a large volume of blood at very low pressures and velocities.
Present a generally thin wall and a large lumen.
Veins
T. adventitia is the thickest layer of the wall.
Veins usually in the extremities have valves to prevent back flow of blood.
Veins
Veins Classified into four major groups according to size a
Venules, small veins, medium veins and large veins.
Venules
-Continuations of capillaries.
-The smallest vessels of the venous circulation.
-Wall consists of an endothelial cell lining surrounded by a loose CT.
-Occur in company of arterioles.
-Classified as small, medium and large venules, based on their size.
Venules
Continuations of venules.
Wall tunics are typical except that the elastica interna is absent and the t. adventitia is thicker than the i. media.
Those located below the level of the heart are provided with valves.
Small veins
Continuations of venules.
Wall tunics are typical except that the elastica interna is absent and the t. adventitia is thicker than the i. media.
Small veins
Continuations of small veins.
Presents valves, especially the medium sized veins in the extremities, as they have to lift blood against gravity.
Medium veins
Continuations of medium veins.
Similar in structure to medium veins except that they have larger diameters relatively thicker walls, and have elastica Interna.
Large veins
are absent in large veins, particularly in the vena cava and hepatic portal vein.
Valves
Short, usually unbranched coiled vessels that directly connect arterioles and venules.
Arteriovenous Anastomoses
When the anastomoses are closed, blood is shunted to the
capillary network.
When the anastomoses are open, blood is shunted directly to the
venous circulation, by passing the capillary network.
Arteriovenous Anastomoses found in the ?
intestine, lips, salivary glands, reproductive tracts, nasal mucosa and skin.
Specialized structures that monitor changes in the blood chemistry (chemoreceptors) and blood pressure (baroreceptors).
Sensory Receptors in the Cardiovascular System
There are two (2) sensory receptors:
There are two (2) sensory receptors:
carotid body and carotid sinus.
Chemoreceptor located in the area of bifurcation of the common carotid artery.
Carotid body
A small encapsulated nodule containing two types of cells:
type I cells or Chemoreceptor cells or glomus cells
type II cells or sustentacular cells.
A small encapsulated nodule containing two types of cells:
type I cells or Chemoreceptor cells or glomus cells
type II cells or sustentacular cells.
Associated with afferent and efferent nerve endings.
Occur in small groups partially surrounded by type II cells.
Type I cells
Large cells with round nucleus and cytoplasmic granules containing
catecholamines and serotonin.
Small spindle-shaped cells with dense oval nucleus and occasionally, a few cytoplasmic granules.
Type II cells
A dilated portion of the internal carotid artery at its origin from the common carotid artery.
Carotid sinus
Wall is typical of an artery except that its t. media has fewer smooth myocytes and more collagen and elastic fibers and the t. adventitia presents afferent nerve terminals from
glossopharyngeal nerve (CN IX).
The afferent nerve terminals are –
that when stimulated by increased blood pressure cause reflex bradycardia, dilation of splanchnic blood vessels and a lowered systemic blood pressure.
mechanoreceptors
The lymphatic system together with the cardiovascular system forms a functional unit called the
hemolymphatic system
The lymphatic system is composed of
lymphatic organs and lymphatic vessels.
Parenchymatous organs that produce lymphocytes.
Lymphatic Organs
Lymphatic Organs Classified as
primary and secondary lymphatic organs
Lymphatic organs that initially produce lymphocytes in the embryo and young animals.
They degenerate at the onset of puberty.
Primary Lymphatic Organs
There are two (2) primary lymphatic organs:
thymus and Bursa of Fabricius.
Primary lymphatic organ in mammals.
A lobulated lymphoepithelial organ.
Capsule is loose CT.
Thymus
Each thymic lobule presents an outer cortex and central medulla
Medulla presents distinct acidophilic bodies called the
Thymic corpuscles (Hassall’s corpuscles)
Thymic corpuscles only are found in
mammals
Thymic cell types :
thymocytes (T lymphocytes),
macrophages
epithelio-reticular cells
stellate cells
Natural involution is irreversible.
Thymus
In birds it completely involutes in 13-17 months of age.
Present only in birds.
Equivalent to the aggregated lymphatic nodules of the ileum in mammals that also produce completely immune-competent B lymphocytes.
Bursa of Fabricius
Differs from other lymphatic organs because instead of being a parenchymatous organ, it is a blind sac on the
dorsocaudal side of the cloaca and opens into the cloaca.
Because of its relationship with the cloaca, it is also called
cloacal tonsil.
The folds are lined by simple columnar or pseudostratified columnar epithelium
Lymph nodules with cortex and medulla, are located in between the folds.
Bursa of Fabricius
The main function is to produce B lymphocytes.
Like the thymus it involutes with the onset of puberty.
Bursa of Fabricius
Absent in birds except swamp, sea and shore birds.
The most organized of the lymphatic organs.
Lymph node
Bean-shaped or oval and enclosed by a capsule of loose and/or dense CT rich in reticular fibers.
Lymph node
Presents afferent lymphatic vessels that penetrate the capsule on the convex surface and efferent lymphatic vessels that leave the hilus or concave surface.
Lymph node
Parenchyma is divided into two regions
outer cortex and central medulla.
Contains the bulk of the lymphatic tissue, both diffuse (DLT) and nodular (NLT).
Structure of the cortex
Contains DLT (lymphocytes and macrophages) in the form of medullary cords with open spaces (medullary sinuses) between them.
B lymphocytes are the dominant cell type in the lymph node.
Structure of medulla:
Found along major muscular arteries
Derived from muscular arteries during embryonic development, as cul-de- sacs, blind pouches.
Considered as an ‘accessory spleen!’
Hemal Node
No afferent and efferent lymphatic vessels because it has no connection to the lymphatic system.
Present in ruminants and in man where they occur in the prevertebral peritoneal tissue, root of mesentery and near the pelvic rim.
Present in ruminants and in man where they occur in the prevertebral peritoneal tissue, root of mesentery and near the pelvic rim.
Also called hemorrhagic lymph node
Similar in structure to the lymph node except that its medullary sinuses contain blood and lymph
Hemolymph node
Present only in ruminants.
Hemolymph node
Really a part of the circulatory system, always described with the lymphatic organs because of the very large population of lymphocytes found in it.
Spleen
Tongue-shaped or leaf-shaped in mammals and
small and round in birds.
No afferent lymphatic vessels; only efferent lymphatic vessels are present.
Involved in hematopoiesis, blood filtration and destruction of old RBCs
Spleen in the The parenchyma consists of
while pulp and red pulp
White Pulp
Consists almost entirely of lymphocytes, in association with the arterial blood supply
Splenic corpuscle
Splenic arteriole
Periarterial sheath
Made up of a pale centrally located germinal center and dark peripheral mantle layer or zone.
Splenic corpuscle
Splenic arteriole
Inappropriately called central, artery because it is not an artery but an arteriole.
Occupies a central or paracentral position in the splenic corpuscle.
Surrounded by the periarterial sheath.
Splenic arteriole
A sleeve of lymphocytes arranged along the splenic arteriole and blends with the mantle layer of white pulp.
Periarterial sheath
Gets its appearance from the firmed elements of the blood (mostly erythrocytes) it contains.
Fills the bulk of the spleen’s volume.
Red Pulp
Anastomosing cords of erythrocytes, lymphocytes and macrophages separated by sinuses; corresponds to medullary cords of lymph node.
Splenic cords (Billroth cords)
Tiny venous spaces between splenic cords.
Contain a few erythrocytes and the normal circulating white blood cells.
May be lined by phagocytic cells and therefore called sinusoids.
Blood sinuses
Splenic artery enters at the hilus of the spleen via the splenic capsule and breaks up into capsular and trabecular arteries
Splenic Circulation
run in bundles resembling hairs of a paintbrush (the Latin word for a paint brush is penicillium).
Penicillar arterioles
run in bundles resembling hairs of a paintbrush (the Latin word for a paint brush is penicillium).
Penicillar arterioles
Sometimes called “arteries of the red pulp.”
Penicillar arterioles
Open circulation theory
Capillaries open right into the splenic cords.
Blood thus passes through the cords and into the adjacent sinuses.
There is no direct connection between the arterial and venous sides, and that the cords act as “filters” through which the total volume of blood has to pass before returning to the venous circulation.
Open circulation theory
Capillaries join the sinuses directly.
Cells in splenic cords get there from the blood passing through the sinusoids.
Both open and closed circulations exist simultaneously.
Compromised theory
Types of Spleen
Defensive type
Storage type
Intermediate type
spleen with few trabeculae but abundant white pulp. Example is the spleen of man.
Defensive type
spleen with many trabeculae and few, large white pulp. Examples are the spleens of horse, dog and cat.
Storage type
spleen with more or less equal number and distribution of white pulp and trabeculae. Examples are spleens of ruminants and swine.
Intermediate type
Very small lymphatic organ present only in birds located under the eye.
Hardenian Gland
are tubular structures that collect and transport lymph from body tissues to the heart.
lymphatic vessels
The wall is very similar to that in veins.
