Cardiovascular Histology

Question 1

metarteriole

Answer 1

narrow vessel surrounded by large, isolated bundles of smooth muscle initial portion surrounded by additional smooth muscle cells, which form a precapillary sphincter that regulates the blood flow through the capillary bed

Question 2

thoroughfare channel

Answer 2

central channel in the arteriolar system

Question 3

endocardium

Answer 3

-inner layer of the heart -lines the ventricles and atria completely and covers the cardiac valves and associated structures -continuous with the tunica interna of the large blood vessels entering and leaving

Question 4

myocardium

Answer 4

• middle and thickest layer of the heart
• composed of bundles of cardiac muscle cells, branches of cardiac conduction fibers, an extensive capillary network, and the cardiac skeleton

Question 5

epicardium

Answer 5

• outer surface of heart (visceral serous pericardium)
• covers myocardium externally
• outermost layer is mesothelial cells, which line the pericardial cavity and secrete serous fluid
• supported by dense connective-tissue layer rich in elastic fibers and adipocytes with blood vessels

Question 6

subendocardial layer

Answer 6

-loosely arranged collagen and elastic fibers -adipose cells may be present, along with a rich supply of blood and lymph vessels and connective tissue that is continuous with that of the myocardium -in some locations, modified cardiac muscle cells of the cardiac impulse conduction system are present

Question 7

fibrous cardiac skeleton

Answer 7

three parts

1) the fibrous rings (annuli fibrosi)
- composed of intermingling bundles of collagen and a few elastic fibers that surround the atrioventricular, aortic, and pulmonary trunk openings
2) the fibrous triangles (trigona fibrosa cordis)
- small areas of connective tissue that fill the spaces between the atrioventricular openings and the base of the aorta
3) the fibrous (or membranous) part of the interventricular septum
- collagen fiber bundles

Question 8

intercalated disks

Answer 8

connects individual cardiomyocytes through junctions like gap, anchoring and desmosomes

support synchronised contraction of cardiac tissue

Question 9

6 microscopic features of the myocardium

Answer 9

• cross striated
• central single nucleus
• intercalated disks
• lipofuscin
• sarcoplasmic reticulum
• many mitochondria

Question 10

Os Cordis

Answer 10

from fibrous trigone area undergoing osseous differentiation

primarily seen in cattle

Question 11

tunica intima

Answer 11

Innermost endothelium of vessels

has an internal elastic membrane and subendothelial connective tissue

Question 12

tunica media

Answer 12

middle smooth muscle layer of vessels

contains elastic lamellae/fibers

Question 13

tunica adventitia (externa)

Answer 13

outermost connective tissue layer of vessels

principally collagen

may contain blood vessels, nerves, and capillaries

Question 14

What does the vascular endothelium do besides act as a barrier?

Answer 14

it is an important mediator of fluid distribution, hemostasis, inflammation, and healing

Question 15

Tunica media

Veins vs Arteries

Answer 15

muscular tunica media of veins is thinner than that of arteries

smooth muscle fibers have an irregular orientation, approximately circular

Question 16

What type of artery is the Aorta? Describe its layer.

Answer 16

Example of an elastic artery

Tunica media - largely repeating elastic lamellae

Tunica intima - endothilium and loose connective tissue

Tunica adventitia - contains vasa vasorum

Question 17

What type of artery is the femoral artery? Describe its layers?

Answer 17

Muscular Artery

media - primarily smooth muscle and is the thickest tunic

generally round appearance in cross section

prominant internal elastic membrane

Question 18

vascular smooth muscle

Answer 18

regulates diameter and tone (vasodilation/constriction)

smooth muscle cells are circumfrentially arranged within tunica media

Question 19

arterioles

Answer 19

1-3 layers of smooth muscle

Greatest effect on blood pressure

Nuclei bulge into lumen

Round appearance of vessel

No internal elastic membrane in the smallest arterioles with 1 smooth muscle cell

Question 20

Pericytes (Rouget cells)

Answer 20

Mesenchymal-like contractile cells (contain actin, myosin, tropomyosin)

wrap around capillaries and venules and communicate” with endothelial cells by physical contact and paracrine signaling

Have own basal lamina. Proliferate after injury. May be replacement stem cell source. Important in angiogenesis - new vessels formation

Question 21

Carotid bodies

Answer 21

Specialized vascular sensors found at origin of internal carotid artery

epithelioid cells that are CHEMORECEPTORS (O2 , CO2 , pH)

Question 22

Carotid sinuses

Answer 22

specialised vascular sensors

BARORECEPTOR nerve endings of Cranial Nerve IX

Question 23

Aortic bodies

Answer 23

specialised vasular sensors

CHEMORECEPTORS found within the wall of the aorta

Question 24

capillaries

Answer 24

Thin walled tubules of mesenchymal origin

in a cross section they are made of only one endothelial cell rolled into the tube

site of exchange between blood and surrounding tissue

diameter is 7–9 µm, the length 0.25 – 1mm, in some organs (adrenal cortex, kidney medulla) can be up to 5-10 cm long.

Question 25

Continuous capillaries

Answer 25

virtually ubiquitous in the organism

tight junctions

few mitochondria and ribosomes

little endoplasmic reticulum

small Golgi complexes

Transcytotic vesicles may be either numerous, as in muscular capillaries or scarce to nonexistent, as in neural capillaries.

Question 26

Fenestrated capillaries

Answer 26

commonly occur in the gastrointestinal tract

large diameter

fenestrations facilitate the passage of substances across the endothelium

Question 27

Sinusoids

Answer 27

are present in the liver, bone marrow, and certain endocrine glands

larger than other capillaries

shape themselves to fill the space within the confines of the surrounding parenchyma

Large intercellular openings and pores surrounding basal lamina, provide for a maximum exchange between blood and surrounding parenchyma.

Phagocytic cells often span the lumen of sinusoids or lie just outside the endothelium.

Question 28

What type of capillaries are in the glomerulus?

Answer 28

fenestrated capillaries responsible forthe filtration of plasma

Question 29

Venules

Answer 29

aka POSTCAPILLARY VENULES

Very leaky vessels

NO SMOOTH MUSCLE

LEUKOCYTE diapedesis possible here

5mm Hg pressure in vessel

Question 30

Veins

Answer 30

Large, wide lumen, thin tunica media

Valves present

tunica adventitia is the thickest tunic

large veins may have vasa vasorum

Question 31

lymphatic vessel structure

Answer 31

very thin wall, very low pressure, may contain valves

No RBCs in lymph, appears clear in section