Structures of Blood Vessels and Heart

Question 1

Layers or vessels

Answer 1

tunica intima
tunica media
tunica adventitia

Question 2

Tunica intima

Answer 2

innermost layer
single squamous epithelium lining the lumen
adjacent layer of connective tissue

Question 3

Tunica media

Answer 3

middle layer
smooth muscle, mainly circular
varying amounts of elastin, mainly in sheets in interspersed connective tissue

Question 4

Tunica adventitia

Answer 4

outermost layer
connective tissues with varying amounts of interspersed elastin fibres and smooth muscle cells
mainly longitudinal

Question 5

Similarities and differences of heart struture and vessels

Answer 5

3 layer struture:
endocardium - tunica intima, same but lined with relatively loose connective tissue
myocardium - tunica media, cardiac not smooth
epicardium - tunica adventitia, partially dense and loose, bordered by simple squamous (visceral) - inner lining or pericardial sac

Question 6

What is the myocardium supplied by?

Answer 6

coronary vessels - vasa vasorum

Question 7

Elastic arteries histology

Answer 7

much thicker than intima
intima: simple squamos, thin layer of relatively thin loose connective tissue
media: much thicker than intima sheets of elastin (black wavy lines), for muscle contraction (pulsating blood flow)
smooth muscle cells - contraction due to fixation of tissue
adventitia: mostly loose connective tissue with vasa vasorum, no elastic lamella, few smooth muscle cells, bordered by simple squamous

Question 8

Muscular arteries

Answer 8

help distribute bulk of blood to the site of need

also experiences pulsating flow

Question 9

Muscular arteries structure

Answer 9

elastin sheath that borders intima
tunica media - thick layer of circumferentially arranged smooth muscle cells with interspersed collagen and ver few elastin lamellae
external elastin membrane
tunica adventitia - more longitudinal strings of elastin, mostly loose connective tissue

Question 10

Which blood vessels are the main site of blood pressure regulation?

Answer 10

arterioles, due to biggest site of resistance and therefore decrease in velocity

Question 11

Histology of small artery

Answer 11

intima with internal elastic membrane
media with several circular layers of smooth muscle cells
adventitia undefined
blood flow not pulsating therefore no internal elastic membrane
thins walls, no vasa vasorum needed

Question 12

Arteriole histology

Answer 12

intima and one layer of smooth muscle cells in the media
undefined adventitia
1-3 circular smooth muscle layers
blood flow not pulsating therefore no internal elastic membrane
thins walls, no vasa vasorum needed

Question 13

Capillaries histology

Answer 13

just tunica intima
one layer of endothelial cells, few collagen fibres
cell-cell contact with tight adherens junctions
most are continuous, some have pores (fenestrated)

Question 14

What are sinusoids?

Answer 14

found in liver and spleen
beds of wide capillaries with diametes of several erythrocytes
endothelial cells and basement membranes have ‘holes’ which allow plasma to directly reach, resulting in faster exchange of larger components

Question 15

Venules and small veins role

Answer 15

collect blood from capillary beds

Question 16

Venules in heart muscle histology

Answer 16

larger lumen than capillaries
no muscle cells
tunica intima with endothelial cells and odten pericytes
no media and hardly any adventitia

Question 17

Pressure of venules

Answer 17

flow slightly increased compared to capillaries, lower pressure, enabling flow in their direction

Question 18

What are valves

Answer 18

in veins to prevent backflow of blood due to large pressure gradient
outgrowths of intima

Question 19

What is the muscle pump

Answer 19

rythmic contraction of muscles that helps push venous blood towards the heart due to venous valves
eg. walking

Question 20

Vein-artery-vein triplets

Answer 20

in extremities
muscular arteries accompanied by veins on either side
pulsations slightly compress veins, driving blood towards the heart

Question 21

Methods for pushing blood back towards the heart

Answer 21

muscle pump

vein-artery-vein triplets

Question 22

Histology of muscular veins

Answer 22

intima: endothelial layer with small amount of connective tissue
media: smooth muscle interspersed with collagen, normally thinner than media of muscular arteries
adventitia: loose connective with elastic fibres, few longitudinal smooth muscle strands, some vasa vasorum

Question 23

What is a portal system

Answer 23

connects two capillary beds
eg. portal vein links capillary beds of digestive system and spleen directly to the capillary bed (sinusoids) of the liver

Question 24

Role of lymphatic system

Answer 24

collect and transport fluid leaked from capillary beds back into blood circulation

Question 25

Characteristics of lymphatic system

Answer 25

trees of small vessels that have antigen presenting sites (lymph nodes) at the intersections

Question 26

How to identify lymph vessels

Answer 26

compare to blood vessels full of erythrocytes
they are devoid of them, just have fluid and few leukocytes
thin walls, often embedded into connective tissue