Histology

Question 1

Describe smooth muscle physical characteristics

Answer 1

swollen in the center w/ finely tapered ends; central nucleus that is typically a little elongated but doesn’t get flattened down; no visible striations; interconnected by gap junctions

Question 2

What is the purpose of dense bodies?

Answer 2

equivalent to Z discs that anchor to actin and myosin in smooth muscle cytoplasm

Question 3

What is the purpose of caveolae?

Answer 3

equivalent to T-tubles; small indentations that allow Ca signaling into the cell to create contraction

Question 4

Describe cardiac muscle physical characteristics

Answer 4

short, branched, Y shaped cells w/ extensive capillaries and centrally located nucleus

Question 5

What is the purpose of intercalated discs?

Answer 5

transverse junctions between cardiac muscle cells (where cells meet end to end) that allows for the passage of electrical current

Question 6

What is unique about the organelles in cardiac muscle cells?

Answer 6

organelles and cell fibers loop around the centrally located nucleus to protect it from damage w/ intense cell contraction

Question 7

Describe the layers of the pericardium

Answer 7

Fibrous - outer covering of dense CT
Parietal serous - lines inner surface of fibrous
Visceral serous - covers outer surface of heart (epicardium)
Pericardial cavity - space between parietal and visceral layers

Question 8

Describe the layers of the heart wall

Answer 8

mesothelium - simple squamous epithelium (outer layer)
underlying layer of loose CT and adipose tissue (where coronary vessels usually found)
Myocardium - heart muscle
Endocardium - loose connective tissue and endothelium (simple squamous)

Question 9

What makes up the epicardium?

Answer 9

mesothelium + underlying layer of loose CT and adipose tissue -> much thicker than endocardium

Question 10

Function of fascia adherens?

Answer 10

actin based filaments at ends of sarcomeres that transmit contract forces between cells in a way that prevents damage (most prevalent)

Question 11

Function of desmosomes?

Answer 11

provide anchorage for intermediate filaments of cytoskeleton (prevent tearing of myocardium)

Question 12

Function of gap (nexus) junctions?

Answer 12

sites of low electrical resistance; allows excitation to pass between cells

Question 13

What makes up a Dyad T-tubule? What is its function?

Answer 13

1 T-tubule + 1 SR cisterna (fewer number compared to triad T tubule in skeletal muscle; permits uniform contraction myofibrils within single cardiomyocyte

Question 14

What are lipofuscin granules?

Answer 14

small bodies that accumulate around the nucleus w/ age; material from residual bodies after lysosomal digestion

Question 15

What cells contains ANF and BNF? What is the purpose of ANF?

Answer 15

myoendocrine cells (atrial cardiomyocytes) - ANF targets kidneys to increase filtration rate (decreases Na and H2O retention)

Question 16

What makes endocardium thicker in ventricles compared to atria?

Answer 16

ventricles have subendocardial layer - thin layer of CT w/ smooth muscle that contains Purkinje fibers between myocardium and endocardium

Question 17

Describe the physical characteristics of Purkinje fibers

Answer 17

more rounded than cardiac muscle cells; larger cell and nucleus; some intercalated discs (not many) and mostly lack T tubules

Question 18

What does the cardiac skeleton consist of? What is its purpose?

Answer 18

4 rings (one around each valve) and 2 trigones (broader areas that connect rings to valve; anchors valves and surrounds AV canals to help maintain shape

Question 19

What are heart valves?

Answer 19

extensions of endocardium on either side of opening between chambers that is continuous w/ cardiac skeleton

Question 20

Where is the tunica intima?

Answer 20

layer most closely exposed to the vessel (most internal layer)

Question 21

What are the layers of tunica intima?

Answer 21

endothelium - single layer of squamous epithelial cells
Basal lamina of endothelial cells
Subendothelial layer of loose CT

Question 22

Where would you find the internal elastic membrane (lamina)?

Answer 22

in the subendothelial layer of tunica intima of arteries and arterioles; links tunica intima to tunica media

Question 23

What is found in the tunica media? In what vessels is this layer thick?

Answer 23

circumferentially arranged layer of smooth muscle; relatively thick in arteries

Question 24

Where would you find the external elastic membrane (lamina)?

Answer 24

on the outer border of the tunica media; links tunica media to tunica adventitia

Question 25

What makes up tunica adventitia? How thick is it in arteries and veins?

Answer 25

collagenous loose CT w/ few elastic fibers; relatively thin in arteries and thick in veins/venules

Question 26

What is vasa vasorum and where is it found?

Answer 26

vessels of tunica adventitia; supply blood to vascular walls (vessels of vessels)

Question 27

What is nervi vasorum and where is it found?

Answer 27

ANS input that controls contraction of vascular smooth muscle (nerves of vessels); found in tunica adventitia

Question 28

Describe large (elastic) arteries and the physiology behind its structure

Answer 28

thick tunica media w/ elastin forming sheets/lamellae between muscle cell layers -> elastin allows arterial wall to expand due to high pressures during systole

Question 29

What is prominent in medium (muscular) arteries?

Answer 29

internal elastic membrane is prominent (folds down on itself and looks wrinkly); also has recognizable external elastic membrane

Question 30

How thick is tunica media in muscular arteries compared to elastic arteries?

Answer 30

more smooth muscle and less elastin present in tunica media (less BP); relatively thick tunica adventitia - about same thickness as tunica media

Question 31

How would you distinguish small arteries from arterioles?

Answer 31

small arteries have up to 8 layers of smooth muscle and internal elastic membrane arterioles have 1-2 layers of smooth muscle and internal elastic membrane may not be present

Question 32

What are pericytes and what is their function?

Answer 32

perivascular contractile cells/ branching processes found in capillaries; they are controlled by NO produced by endothelial cells and promote stability of capillaries

Question 33

Describe continuous capillaries

Answer 33

continuous layer of endothelial cells surrounded by basal lamina; only small substances (gases etc.) can diffuse

Question 34

Describe fenestrated capillaries

Answer 34

endothelial cells have pores that allow larger material to diffuse but with restrictions; basal lamina continuous; located in places we want filtration (kidneys)

Question 35

Describe sinusoidal capillaires

Answer 35

no regulation; pores are large enough for full cells to fit through and basal lamina is discontinuous; found in bone marrow and liver

Question 36

Where would you find endothelial cells? What are their functions?

Answer 36

innermost layer of tunica intima (lining vessel wall); they support basement membrane and produce collagen; also involved in coagulation and local vasodilation/constriction

Question 37

What is a metarteriole?

Answer 37

first branch off arteriole to capillary bed

Question 38

What is a true capillary?

Answer 38

branch from metarteriole that lacks smooth muscle but may have pericytes

Question 39

What is a thoroughfare channel?

Answer 39

distal end of metartiole that connects to post capillary venule; lacks smooth muscle

Question 40

What is the function of precapillary sphincters?

Answer 40

to regulate blood through true capillaries; when contracted, they shunt blood flow away from capillary bed -> forces blood to enter venous return quickly

Question 41

What are 2 classifications of venules?

Answer 41

postcapillary - drains capillaries; no true tunica media | muscular - 1-2 layers of smooth muscle in tunica media

Question 42

How would you describe small veins?

Answer 42

continuous w/ muscular venules but they have all 3 layers w/ a thicker tunica adventitia

Question 43

What do medium veins travel with? What makes them different from venules/small veins?

Answer 43

they travel w/ muscular arteries and contain valves

Question 44

What are examples of large veins? What is their thickest layer?

Answer 44

superior/inferior vena cava, hepatic portal vein; their thickest layer is tunica adventitia but overall, wall is thinner than arteries

Question 45

Describe the internal structure of lymphatic capillaries

Answer 45

closed-ended tubes in the capillary bed; overlapping endothelial cells form a 1-way valve for collecting lymph

Question 46

What is the flow of lymphatics?

Answer 46

lymphatic capillaires -> vessels -> trunks -> right lymphatic duct -> thoracic duct drains into brachiocephalic veins