Cardiavascular Histology Flashcards
Cardiac tunics
Endocardium
Myocardium
Epicardium
Endocardium
- Innermost layer, lining the atria and the ventricles
- components: endothelium, subendothelial CT
- Continuous with the tunica of the blood vessels entering and leaving the heart
- Subendocardium is layer located between the endocardium and the myocardium
- contains nerves and purkinje fibers (subendocardial fibers)
A layer located between the endocardium and the myocardium
Subendocardium
The subendocardium contains
nerves and purkinje fibers (subendocardial fibers)
Purkinje fibers
- Large, specialized cardiac muscle cells
- Carry impulses to ordinary cardiomyocytes
Myocardium
Consists of cardiac muscle cells
Epicardium
- External surface is covered by simple squamous epithelium (mesothelium)
- Mesothelium overlies fibroelastic CT containing adipose cells, nerves, and coronary vessels
The epicardium’s external surface is covered by
simple squamous epithelium (mesothelium)
What is mesothelium
-The simple squamous epithelium covering the external surface of the epicardium
The cardiac Skeleton
- Dense collagenous CT
- Myocardial fibers originate and insert into the cardiac skeleton
Wall of all blood vessels except the capillaries are characterized by
three layers (tunics)
Components of the tunica intima
- Endothelium and its basal lamina
- found in all arteries and arterioles
- endothelial cells produce von Willebrand’s factor VIII
- Subendothelial CT
- found in all elastic and muscular arteries and some arterioles
- Internal elastic membrane
- incomplete in elastic arteries but thick and complete in muscular arteries
The tunica media is mad up of
- circular smooth muscle tissue and fibroblasts
- contains collagen and elastic fibers
Tunica media contains
collagen and elastic fibers
The tunica Adventitia
- outermost layer
- lacking in arterioles
- consists of loose areolar tissue
- contains irregular fibroelastic tissue with adipocytes
- has small vessels (vasa vasorum) and nerves (nervi vasorum)
The tunica adventitia is not present in
Arterioles
The tunica adventitia consists of
loose areolar tissue
Tunica adventitia contains
irregular fibroelastic tissue with adipocytes
What is the vasa vasorum and neri vasorum
-small vessels and nerves that are present in the tunica adventitia
What are the conducting arteries
the more elastic arteries
What are the distributing arteries
The more muscular arteries
Pressure ____ as arteries leave the heart and become progressively smaller
drops
Elastic arteries
- Conducting arteries
- Stretch during systole and recoil during diastole
- tunica media consists of layers of elastic fibers organized into elastic laminae:
- 40 layers in newborn to 70 layers in older adult
- CT is interspersed between the elastic laminae
- Include: Aorta, pulmonary trunk, large branches of aorta
The elastic arteries include
- Aorta
- pulmonary Trunk
- Large branches of the aorta
Tunica media of elastic arteries consist of
- layers of elastic fibers organized into elastic laminae
- 40 layers in newborn to 70 layers in older adults
- CT is interspersed between the elastic laminae
Muscular Arteries
- Distributing arteries
- Tunica media consists of smooth muscle that responds to autonomic stimulation and hormones:
- Thickness of smooth muscle layer decreases as diameter becomes smaller
- Gradual transition form elastic artery to muscular artery
- Include: All named arteries of the body except the elastic arteries
The tunica media of muscular arteries
consists of smooth muscle that responds to autonomic stimulation and hormones:
- thickness of smooth muscle layer decreases as diameter becomes smaller
- Gradual transition from elastic artery to muscular artery
Muscular arteries include
all named arteries of body except for the elastic arteries
The smooth muscle cells of the tunica media in muscular arteries produce
elastic, reticular, and collagenous fibers
Arterioles
- Small arteries
- Tunica media consists of one to three layers of smooth muscle cells
- Mean arterial pressure depends on proper tone of smooth muscles in arterioles (peripheral resistance arterioles)
- Thickness of smooth muscle layer decreases as diameter becomes smaller
- Gradual transition from elastic artery to muscular artery
- Give rise to metarterioles which have a discontinuous layer of smooth muscle tissue
The tunica media of arterioles consists of
1 to 3 layers of smooth muscle cells
Arterioles give rise to metarterioles which have a _______ layer of smooth muscle tissue
discontinuous layer
Mean arterial pressure of arterioles depend on
- proper tone of smooth muscles in arterioles (peripheral resistance arterioles)
- Thickness of smooth muscle layer decreases as diameter becomes smaller
- gradual transition from elastic artery to muscular artery
Perictes
- Undifferentiated mesenchymal cells
- may be contractile
- may serve as stem cells to differentiate into fibroblasts, etc
Continuous capillary
Endothelial cells have a complete (continuous) cytoplasm. This type is found in muscle, brain, thymus, bone, lung, and other tissue
The cardiovascular system consists of
-Heart and the vessels that make up the circulatory system
Where are continuous capillaries found
- muscle, brain, thymus, bone, lungs, and other tissues
Where are fenestrated capillaries found
- intestines, endocrine glands, and around kidney tubules
Fenestrated capillaries
the endothelial cell has many finest (10 to 100nm) with or without a thin diaphragm. The basal lamina is continuous
Discontinuous capillaries
The gaps in discontinuous capillaries are larger than in fenestrated capillaries. The basal lamina is discontinuous
Discontinuous capillaries are found in the
spleen, liver
Pericytes can occur where
between the endothelium and the basal lamina of continuous capillaries
Where are fenestrated capillaries without a diaphragm found
in the renal glomerulus
Veins in comparison with arteries
- Larger lumen
- Thinner wall
- Valves are present in many veins
Larger veins have a layer of
longitudinal smooth muscle in the inner aspect of the tunica adventitia
The major organizational theme of the histology of the heart and blood vessels is that they are all constructed on the basis of
three specific layers, or tunics
The muscular tunica media of veins structure compared to arteries
thinner than that of arteries. Smooth muscle fibers have an irregular orientation, approximately circular
What are valves
projections into the lumen of the tunica intima. They are covered by endothelial cells and have a core of elastic fibers
Veins contain about ____ percent of the total volume of blood
70%
Varicose veins result from intrinsic weakness of the
muscular tunica media caused by increased intraluminal pressure or form defects in the structure and function of the valves.
most common places for varicose veins
- Sapenous veins of the legs
- Veins in the anorectal region (hemorrhoids)
- The veins of the lower esophagus (esophageal varices)
- Veins in the spermatic cord (varicocele)
Characteristics of lymphatic capillaries
- single layer of endothelial cells
- basal lamina may be absent
- Anchoring filaments
- Valves in larger lymphatics
What is the function of prostacyclin
- formed by endothelial cells
- prevents adhesion of platelets to the endothelium, thus avoiding clot formation
Formation of an atherosclerotic plaque
- ) Endothelial cell dysfunction- damage to endothelium of an artery, caused y hypercholesterolemia, is followed by homing of blood monocytes in the tunica intima after adhesion to vascular cell adhesion molecule-1 (VCAM-1). In the intima, monocytes change into macrophages expressing scavenger receptor-A (SR-A) that internalizes modified cholesterol-rich low-density lipoprotein (LDL), LDL-containing multilocular deposits give macrophages a foamy appearance
- ) Formation of the atherosclerosis plaque- developed in the intimal consists of an atheroma core with abundant macrophages foamy cells and a fibrous cap
- ) T cells-macrophage interaction- VCAM-1 mediated homing of T cells contributes additional inflammatory components to the atherosclerotic plaque. T cell-macrophage interaction results in the production of metalloproteinases (MMPs) by macrophages and pro inflammatory cytokines by T cells
- ) Fracture of the plaque and thrombosis- MMPs and inflammatory cytokines weaken and fracture the fibrous cap. The thrombogenic potential of the plaque, resulting from the production of procoagulant tissue factor by macrophages, causes thrombosis leading to the obstruction or occlusion of the arterial lumen
The internal elastic membrane is ____ in elastic arteries but thick and ______ in muscular arteries
incomplete, complete
