Cardiovascular 1 Flashcards
What are the examples of elastic arteries?
-aorta and it’s main branches, common carotid, Subclavian, common iliac
Why are named elastic arteries larger?
Due to the number of elastic fibers in tunica media (40-70 layers)
What are the main characteristics of elastic arteries?
Imbricated: the elastic fibers are arranged in concentric layers like shingles on the roof.
Have fenestrations-permitting diffusion of nutrients
Vascular smooth muscle between layers of elastic fibers
Clinical: Marfan syndrome
What is the structural significance of elastic arteries?
- expansion of vessel wall to accommodate the large volume of blood during systole
- elastic recoiling to maintain intra vascular pressure
Differentiate the layers of the elastic artery
T. Intima: endothelial cells, sub endothelial connective tissue, IEL not conspicuous
T. Media: 40-70 layers of elastic lamellae, smooth muscle cells, type 3 collagen
T. Adventitia- dense irregular connective tissue. Prevents excessive expansion of vessel
Describe the T media within an elastic artery (such as the aorta)
- Large amount of elastic fibers in tunica media- imbricated arrangement
- Note smooth muscle cells between elastic fibers (elongated nuclei)
What are the examples of muscular arteries?
All medium sized vessels that are named+ brachial, radial, femoral, tibial, etc
What are muscular arteries also known as?
Also refferred to as distributing arteries/named arteries
Most abundant in the body
What is the main differentiation of muscular arteries?
Named muscular arteries- as they contain more smooth muscles in the tunica media than elastic fibers
As they become smaller than elastic arteries, they lose the elastic fibers, which now form external elastic lamellae (EEL) between tunica media and adventitia
-EEL is characteristic of muscular arteries
What is the structural significance of muscular arteries?
Serves as a muscular conduit to distribute blood from elastic vessels to smaller vessels
Describe the tunica intima of the muscular artery
Distinct internal elastic artery
A distinguishing characteristic - undulating (scalloped) appearance
Describe the tunica media
8-40 layers of smooth muscle cells arranged in circular fashion
-few elastic fibers & collagen
Distinct external elastic lamina
Describe the tunica adventitia of a muscular artery
Dense connective tissue with collagen & elastic fibers
-vasa vasorum and nerves
Describe the tunica intima of a small artery
Endothelial cells, minimal sub endothelial connective tissue
IEL- present
Describe the tunica media of a small artery
3-8 layers of smooth muscle cells, arranged in circular fashion
Describe the tunica adventitia of the small artery
Connective tissue with type 1 collagen, I’ll-defined, blends with surrounding connective tissue
Describe arterioles
Smallest arteries- below 0.1 mm in diameter-can be closed down to generate high resistance to flow (resistance vessels) major determinants of blood pressure (R inversely proportional to 1/D^4)
What is the tunica intima of the arterioles comprised of?
Endothelium
Describe the tunica media of the arteriole
1-2 layers of smooth muscle cells
Describe the tunica adventitia of arteriole
Ill defined: merges with surrounding connective tissue
What is the significance of arterioles?
Their small radius provides increased resistance to flow of blood, thereby maintaining the blood pressure
What is the function of the precapillary sphincter?
Regulated the flow of blood into the capillary bed, as per physiological demands
What are the examples of precapillary sphincter function?
- Blood flow increased to G.I. tract after food intake & at the same time decreased flow to other areas of the body
- increased blood flow to skeletal muscles during exercise
What are capillaries ?
Luminal diameter 7-9 microns
Single layer of endothelial cells + basal lamina
Permits exchange of marterial
Different levels of metabolic exchange
May be encircled by pericytes (Rouget cells)
What are continuous/ somatic capillaries?
- Continuous basal lamina
- Uninterested endothelium
- Tight junctions present between cells
What is the significance of somatic/ continuous capillaries?
- complete control over diffusion, endocytosis, and exocytosis
- vessels that form barriers in organs such as brain, thymus, lung, testis, etc.
What are the locations of somatic/continuous capillaries?
- connective tissue
- muscle tissue
- Nerve tissue
- exocrine glands
- cerebral cortex
What are fenestrated/visceral capillary ?
Continuous basal lamina
- Tight junctions present between endothelial cells
- Fenestrations of about 80-100 nm in diameter on endothelial cell membrane
Numerous pinocytosis vessels
What is the significance of continuous/somatic capillaries?
-presence of thin, non-membranous diaphragm across the fenestrations (exception-Glomerular capillaries of kidney)
What is the locations of fenestrated/visceral capillaries?
- peptide-secreting endocrine organs
- ciliary process (eye)
- choroid plexus (ventricles)
- kidney-glomeruli
- lamina propria GIT
What are discontinuous/sinusoidalcapillarues?
- discontinuous basal lamina
- absence of tight junction between the cells
- presence of large fenestrations
- separated by wide, irregular, intercellular gaps
What is the significance of discontinuous/sinusoidal capillaries?
- fenestrations: large and variable-reach several microns
- size of fenestrations vary in different organs
- allow passage of macrmolecules
What are the locations of discontinuous/ sinusoidal capillaries?
- liver
- spleen
- bone marrow
What are the functions of post capillary venues?
Post capillary venules collect blood from the capillary network
Possess an endothelial lining, basal lamina and pericytes
Principal site of vasoactive agents -histamine
What are the unique structures of post capillary venules?
- high endothelial venules- post capillary venules in lymphatic system
- prominent cuboidal endothelial cells, ovoid nuclei
- loosest ZO (zonula occludens)
Inflammation: leukocyte exudation
How are high endothelial cells visualized/recognized in imaging?
They are cuboidal in nature, therefore these vessels are called HEV (high endothelial vessels)
They possess the loosest junctional complexes
What is the function high endothelial vessels?
Facilitate the entry of immune cells from the lumen into connective tissue
Migration occurs during inflammation & also a normal phenomenon in locations such as lymph nodes
What is the homing effect?
HEV(high endothelial vessels) play an important role in “homing effect” in lymphoid organs like lymph node. This is the site where lymphocytes enter a lymph node from circulation.
What is the significance of high endothelial vessels?
These vessels are ports of entry for lymphocytes into lymphatic organ, recruit lymphocyte
What are the characteristics of muscular venules?
- located distal to post capillary venules
- 1-2 of vascular smooth muscle tunica media
- thin tunica adventitia
- no perocytes
What are the characteristics of veins?
-by presence of valves, which are folds of t. intima, supported by fibro-elastic connective tissue, these prevent the back flow of blood
Describe the tunica intima of a large/muscular vein
Endothelium, subendothelial connective tissue
Describe tunica media of a large (muscular) vein
Thin circularly arranged smooth muscles, connective tissue, collagen fibers, fibroblast
Describe the tunica adventitia of large/muscular vein
Thickest layer, longitudinal smooth muscle bundles, collagen , elastic fibers, fibroblasts
What is the lymphatic system?
Returns excess tissue fluid to circulation
How does the lymphatic system start?
Starts off as blind- ended lymphatic capillaries and. Empty into circulation: (unidirectional) valves:
What is lymph flow like?
Flow is sluggish and aided by contraction of adjacent skeletal muscles
What are the characteristics of the lymphatic system?
- Bundles of filament anchor vessels to surrounding CT
- No clear cut separation into tunics
- Lack tight junctions: proteins and large molecules return to vascular compartment
- Not present in Nervous tissue, bone marrow and cartilages
- Impaired function: edema
Describe the Structure of capillaries of the lymphatic system
Tubes of endothelium, no continuous basal lamina, high permiability
What is hypertension?
Can cause damage to smaller blood vessels by scarring, hardening, narrowing of blood vessels and eventually become less elastic
Arterioles- major determinant of blood pressure
What are the 3 characteristic changes in muscular arteries in hypertension?
- Symmetrical hypertrophy of the muscular media, M
- Extensive reduplication of the internal elastic lamina, E
- Fibrotic thickening of the internal In.
All these changes lead to reduction in diameter of the lumen. It can both. Predispose and accelerate development of atherosclerosis
What is atherosclerosis?
- Characterized by lesions of the T. Intima called atheroma or fibro fatty plaques that protrude into and obstructs the vascular lumen-also weakening the underlying the T. media
- “hardening of arteries” - arteriosclerosis (old age). Arteriosclerosis not to be confused with “artherosclerosus”
Explain the histopathogenesis of artherosclerosis
- LDL in the blood contains triglycerides and lipids. These are insoluble in water medium of blood
- When there is excessive LDL, the endothelial cells produce free radicals which oxidize this LDL.
- This oxidized product now initiates migration of monocytes into the tunica intima, which now become macraophages.
- Smooth muscle cells (SMC) also migrate from T intima (subendothelial CT)
- SMC and macrophages engulf oxidized LDL to form foam cells
- SMC proliferate and secrete collagen and other ECM- thickens T intima forming fatty streaks
- Cytokines from the SMC converts these fatty streaks into fibrofatty plaques- which bulges into the lumen and also compresses the Tmedia.
- Results- luminal obstruction: &. Weakened vascular walls (aneurysm)
Explain the pathology of an aneurysm
Aortic aneurysm most commonly affects the thoracic aorta, with the vast majority of cases associated with hypertension and a smaller number associated with connective tissue disorders(e.g. Marfan syndrome)
-A laceration of the tunica intima In leads to tracking of blood into tunica media M. The plane of cleavage (dissection) is usually between the middle and outer thirds of the media.
In the example given, the medial hematoma H frequently burst through the tunica adventitia A with rapidly fatal consequences
What are varicose veins?
- Caused by increased intraluminal pressure and to a lesser extent, loss of support by the vessel wall
- superficial veins of the leg are by far the most frequently involved.
What are the main sites of varicose veins?
Legs, anorectal (hemorrhoids), spermatic cord (varicocele), esophageal vessels
What are causes of lymphedema?
Trauma Post surgical Post radiation Inflammation Parasitic obstruction Obstruction due to metastasis
What are The types Of lymphedema ?
Penoscrotal lymphedema
Filarial
Obstruction to lymphatics
Gf
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