Histology

Question 1

Which two related systems does the CVS consist of?

Answer 1

Circulatory

Lymphatic

Question 2

What are the roles of the circulatory system?

Answer 2

Transport of O2 and nutrients to tissues
Transport of CO2 and waste from tissues 
Temperature regulation 
Distribution of hormones and immune cells 
Reproductive function in males

Question 3

Where is the most of the blood in the body found?

Answer 3

Peripheral veins

Question 4

What are the three layers of blood vessels?

Answer 4

Tunica Intima
Tunica Media
Tunica Adventitia

Question 5

What makes up the tunica intima?

Answer 5

Single layer of squamous epithelium (Endothelium) supported by a basal lamina and a thin layer of connective tissue

Question 6

What makes up the tunica media?

Answer 6

Predominantly muscle

Significant amounts of elastic tissue in areas

Question 7

What makes up the tunica adventitia?

Answer 7

Supporting connective tissue

Question 8

What are the elastic arteries?

Answer 8

The very largest arteries

e.g. Aorta

Question 9

What is the histology of the elastic arteries?

Answer 9

Many sheets of elastic fibres in their tunica media (for elastic recoil)

Question 10

What is the vasa vasorum and why is it needed?

Answer 10

Vascular supply to the elastic arteries
Since they are so large, only inner half of the wall can obtain nutrients from the lumen, so they have their own vascular supply

Question 11

What is the histology of the muscular arteries?

Answer 11

Tunica intima extends to an internal elastic membrane

Between the tunica media and tunica adventitia is an external elastic membrane

Question 12

What is the histology of the arterioles?

Answer 12

Only one or two layers of smooth muscle in tunica media

Almost no adventitia

Question 13

What is the histology of the capillaries?

Answer 13

Essentially composed of endothelial cells and a basal lamina
Often have pericytes at intervals just outside the basal lamina

Question 14

What are pericytes?

Answer 14

Connective tissue cells that have contractile properties

Question 15

What are the three type of capillaries, what is their function and where are they found?

Answer 15

Continuous = Most common. Continuous sheet of endothelial cells. Found in muscle, connective tissue, lung, skin, nerve.

Fenestrated = Found in places where easier access is needed. Have pores in wall. Found in mucosa of the gut, endocrine glands, glomeruli of kidneys

Sinusoidal or Discontinuous = Lack a basal lamina. Large gaps for macromolecules and sometimes cells to pass through. Found in liver, spleen and bone marrow

Question 16

What is the microvasculature of a capillary bed?

Answer 16

Small arteriole connected to a postcapillary venule through a network of metarterioles, thoroughfare channels and capillaries
Precapillary sphincters (composed of smooth muscle) at the beginning of the capillary help control flow through the network

Question 17

What is the histology of a postcapillary venule?

Answer 17

Endothelial cells associates with pericytes, or occasional smooth muscle cells
No continuous smooth muscle layer

Question 18

What commonly occurs at the post capillary venues?

Answer 18

Important sites for exchange (e.g. cells moving into tissue in inflammation), probably because of slowed flow velocity

Question 19

What is the histology of the veins?

Answer 19

Relatively thin tunica media, with continuous band of smooth muscle
Larger veins have large areas of adventitia
Largest veins ace smooth muscle attached to their adventitia

Question 20

What is the histology of the venous valves?

Answer 20

Inward extensions of the tunica intima

Most small to medium sized veins have these valves

Question 21

What are the three layers of the heart (from inside to outside)?

Answer 21

Endocardium
Myocardium
Epicardium

Question 22

What is the histological structure of the endocardium?

Answer 22

Endothelium (specialised simple squamous epithelium)
Basal lamina
Thin layer of collagen fibres
Layer of denser connective tissue
Some areas also have a subendocardium of loose connective tissue containing small blood vessels, nerves and the branches of the impulse conducting system

Question 23

What is the histological structure of the myocardium?

Answer 23

Bundles and layer of contractile cardiac muscle fibres

Individual muscle fibres are surrounded by delicate, collagenous connective tissue with a rich network of capillaries

Question 24

What is the histological structure of the epicardium?

Answer 24

Single layer of flattened epithelium on the surface of the heart (mesothelium)
Basal lamina
Fibroelastic connective tissue and, in some places, adipose tissue

Question 25

Why does much of the epicardium have a layer of adipose tissue?

Answer 25

Large vessels are often found here

Question 26

What is the histology of the fibrous pericardium?

Answer 26

Sac of tough fibrocollagenous connective tissue

Question 27

What is the histology of the serous pericardium?

Answer 27

Made up of a ayer of simple squamous epithelium backed by basal lamina and connective tissue Lines the inner surface of fibrous pericardium (parietal serous pericardium) and covers the heart surface (visceral serous pericardium, or epicardium)

Question 28

What is the histology of the fibrous skeleton of the heart, and what is its function?

Answer 28

Thick bands of connective tissue around the heart valves, between the atria and between the ventricles Connective tissue supports the vales, and also provides attachment for cardiac muscle fibres

Question 29

What is the histology of the heart valves?

Answer 29

Outer endothelial layer with basal lamina Layer of collagen and elastin fibres Core of dense connective tissue (lamina fibrosa) that is in continuity with the fibrous skeleton Leaflets of mitral and tricuspid are anchored by papillary muscles in the wall of the ventricle by collagenous strands of chord tendinae, which merge with the lamina fibrosa No blood supply

Question 30

What are the three types of cardiac muscle cells?

Answer 30

Contractile cells Pacemaker cells Conducting cells

Question 31

What is the histology of contractile cells?

Answer 31

Single central nucleus Striated Smaller than normal muscle cells Intercalated discs allow for communication between cells Gap junctions allow for spread of electrical activity

Question 32

What is the histology of pacemaker cells?

Answer 32

Specialised muscle cells Smaller than contractile cells Embedded in extensive connective tissue matrix Pale due to paucity of organelles within Few, irregularly arrange myofibrils Little glycogen No proper T-tubule system

Question 33

What is the histology of the Purkinje fibres (conducting cells)?

Answer 33

``` Modified muscle cells Larger than contractile cells Found in subendocardial layer Abundant glycogen No T-tubules No intercalated discs Sparse actin and myosin filaments, which tend to be found at the cell periphery Appear pale and often have a very pale/clear centre ```

Question 34

Since lymphatic vessels have no central pump, what produces the flow of lymph?

Answer 34

Smooth muscle in walls Hydrostatic pressure in the tissue Compression fo the vessels by voluntary muscle Valves