Histology

Question 1

Roles of the circulatory system (5)

Answer 1

• Transport oxygen and nutrients to the tissues
• Transport CO2 and other metabolic waste away from tissues
• Temperature regulation
• Distribution of hormones and immune cells
• Reproductive function in males (penile erection)

Question 2

3 layers of blood vessels, from inner layer to outer layer

Answer 2

Tunica intima, tunica media, tunica adventitia

Question 3

Tunica intima:

• What does it consist of?
• What is it separated from the tunica media by?

Answer 3

• Consists of single layer of squamous epithelial cells (endothelial cells) supported by a basal lamina and thin layer of connective tissue
• Layer of elastic tissue called internal elastic membrane

Question 4

Tunica media:

• What is it made up of?
• What is it separated from the tunica adventitia by?

Answer 4

• Made up predominantly of smooth muscle, of which the thickness varies
• Layer of elastic tissue called external elastic membrane

Question 5

Tunica adventitia:

- What is it made up of?

Answer 5

Supporting connective tissues separated by elastic lamina

Question 6

Why are the largest arteries called elastic arteries?

Answer 6

They have many sheets of elastic fibres in their tunica media to provide elastic recoil

Question 7

Arterioles:

• Describe tunica media and adventitia in arterioles
• Typical diameter

Answer 7

• Only one or two layers of smooth muscle in tunica media and almost no adventitia
• 30-200 microns

Question 8

Capillaries:

• What are they composed of?
• Typical diameter

Answer 8

• Endothelial cells and basal lamina

- 4-8 microns

Question 9

Pericytes in capillaries

Answer 9

Connective tissue cells that have contractile properties found at intervals just outside the basal lamina

Question 10

3 types of capillaries

Answer 10

Continuous capillaries (more common), fenestrated capillaries, sinusoidal or discontinuous capillaries

Question 11

Continuous capillaries:

- Where are they found?

Answer 11

Muscle, connective tissue, lung, skin, nerve

Question 12

Fenestrated capillaries:

• What do they contain in their wall?
• Where are the found?

Answer 12

• 50nm pores in the wall

- Mucosa of the gut, endocrine glands, glomeruli of the kidneys

Question 13

Sinusoidal/discontinuous capillaries:

• What do they contain?
• Describe the basal lamina
• Where are they found?

Answer 13

• Large gaps through which macromolecules and sometimes even cells can pass
• Discontinuous or absent basal lamina
• Found in the liver, spleen and bone marrow

Question 14

What do capillary networks drain into and what size are these?

Answer 14

Post-capillary venules which are about 10-30 microns

Question 15

Structure of post-capillary venules

Answer 15

Endothelial lined with a thin layer of connective tissue and occasional pericytes

Question 16

When do post-capillary venules become venules?

Answer 16

Once the vessel begins to acquire intermittent smooth muscle cells in a tunica media layer

Question 17

Size of venules

Answer 17

generally >50 microns

Question 18

Describe tunica media in veins

Answer 18

Relatively thin but continuous tunica media, typically consisting of a few layers of smooth muscle

Question 19

What are valves?

Answer 19

Inward extensions of the tunica intima

Question 20

Tunica media in arteries compared to veins

Answer 20

It is much thicker

Question 21

3 layers of the heart inner to outer

Answer 21

Endocardium, myocardium, epicardium

Question 22

Endocardium:

• What does it consist of??
• Where is it present?

Answer 22

• Consists of a layer of endothelial cells backed by connective tissue
• Lines the entire surface of the heart including the valves

Question 23

Myocardium:

- What does it consist of?

Answer 23

Thick coat of muscle cells and bundles of layers of contractile cardiac muscle fibres

Question 24

What are individual muscle fibres in the myocardium surrounded by?

Answer 24

Delicate, collagenous connective tissue with a rich network of capillaries

Question 25

Epicardium: - What does it consist of? - Where is it?

Answer 25

- A single layer of flattened epithelium called mesothelium, basal lamina, fibroelastic connective tissue and in some places, connective tissue - On the surface of the heart

Question 26

2 parts of the pericardium

Answer 26

Fibrous pericardium and serous pericardium

Question 27

Fibrous pericardium

Answer 27

Sac of touch fibrocollagenous connective tissue

Question 28

Serous pericardium

Answer 28

Simple layer of simple squamous epithelium backed by basal lamina and connective tissue

Question 29

2 types of serous pericardium and what they cover

Answer 29

Parietal serous pericardium - lines inner surface of fibrous pericardium Visceral serous pericardium - covers the surface of the heart

Question 30

Fibrous skeleton of the heart: - What is it formed by? - Where is it? - What does it do?

Answer 30

- Formed by thick bands of fibrous connective tissue - Around the heart valves, between the atria and between the ventricles - Supports the valves and provides attachment for the cardiac muscle fibres

Question 31

Heart valves: | - Outer layer, middle layer and core

Answer 31

- Outer layer endothelial layer with basal lamina - Layer of collagen and elastic fibres - Core of dense connective tissue called lamina fibrosa that is in continuity with the fibrous skeleton

Question 32

3 types of cardiac muscle cells

Answer 32

Contractile cells, pacemaker cells, conducting cells

Question 33

What percentage of cardiac muscle cells are contractile cells?

Answer 33

99%

Question 34

Functions of the fibrous skeleton

Answer 34

Provides physical support to the heart and electrically isolates the atria from the ventricles

Question 35

Where are purkinje fibres found?

Answer 35

Subendocardial layer just deep to the endocardium

Question 36

What do purkinje fibres contain?

Answer 36

Abundant glycogen, sparse actin and myosin filaments which tend to be found at the periphery of cell

Question 37

What do purkinje fibres do?

Answer 37

Distribute excitatory activity such that ventricular contraction generally occurs from inferior to superior

Question 38

Function of the lymphatic system

Answer 38

Drains excess interstitial fluid into the bloodstream

Question 39

What does interstitial fluid contain?

Answer 39

Ions, lipids, protein and occasional cells

Question 40

How is flow produced in lymphatic vessels?

Answer 40

Hydrostatic pressure within the tissue and compression of the tissue by voluntary muscle, combined with valves in the vessels, produce flow