CVS 2.1 - Histology Of CVS Flashcards Preview

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Flashcards in CVS 2.1 - Histology Of CVS Deck (33):

What is the pathway of blood from the capillaries back to the heart?

- Capillaries
- Post Capillary Venules
- Venules
- Medium Veins
- Large Veins
- Heart



What effect does a low cross sectional area have on the rate of blood flow?

Causes a high rate of blood flow


What is the significance of capillaries having a high total cross sectional area?

Causes a slow rate of blood flow therefore ensuring efficient gas exchange


What happens during systole?

- Left ventricle contracts
- Blood pressure in aorta increases (to around 120mmHg)
- Walls of elastic aorta stretch


What happens during diastole?

- Aortic semilunar valve closes
- Aorta walls recoil
- Pressure is maintained and blood is moved towards smaller vessels
- Pressure drops to around 70-80mmHg


What are the three layers of blood vessels?

- Tunica intima (closest to lumen)
- Tunica media
- Tunica Adventitia


Describe the tunica intima of elastic conducting arteries

- Simple squamous epithelium

- Narrow subendothelium of connective tissue


Describe the tunica media of elastic conducting arteries

- Has 40-70 fenestrated elastic membranes

- Smooth muscle and collagen are between lamellae


Describe the tunica adventita of elastic conducting arteries

- Thin fibroelastic connective tissue

- Contains vasa vasorum, lymph vessels and nerve fibres


Describe the tunica intima of muscular arteries

Same as elastic arteries but with the addition of a thick internal elastic Lamina


Describe the tunica media of muscular arteries

- 40 Layers of smooth muscle cells

- Connected by gap junctions


What is the significance of gap junctions in the tunica media of muscular arteries?

There can be quick transmission of depolarisation therefore the cont ratio is coordinated


Describe the tunica Adventitia of muscular arteries

- Same as elastic but vasa vasorum isn't very prominent

- Has unmyelinated nerve endings that release noradrenaline


What is the significance of the unmyelinated nerve endings in the tunica Adventitia?

- Release noradrenaline

- Noradrenaline diffuses through fenestrations of the external elastic Lamina into external tunica media

- Depolarises smooth muscle cells


Describe the structure of an arteriole

- Same three layers
- Tunica media has one smooth muscle cell around all endothelial cells
- No elastic external Lamina
- Tunica adventita is scarce


What is an end artery and what is their significance?

- Terminal artery

- Supply blood to parts without significant collateral circulation e.g. Coronary artery, central artery to retina (absolute end artery)


How are end arteries formed?

Progressive branching without connections with other arteries


What is the function of metarterioles?

To supply blood to and control the rate of flow into the capillary bed


Describe the structure of metarterioles

- Smooth muscle layer is not continuous
- Muscle cells are spaced apart and cover endothelium of the capillary (precapillary sphincter)


What is the function of capillaries?

Gas and nutrient exchange


Describe the structure of the capillary wall

Single layer of endothelium + basement membrane


What are the three types of capillary?

- Continuous
- Fenestrated
- Sinusoidal/discontinuous


Describe a Sinusoidal/discontinuous capillary. Where can they be found?

- Larger diameter so slower blood flow
- Gaps in walls so whole cells can move between blood and tissue
- Liver, spleen and bone marrow


Describe a post capillary venule

- Similar wall to capillaries
- More permeable than capillaries
- Fluid drains in due to the decrease in pressure, except for inflammatory responses


Describe a venule

- Tunica media begins to appear

- Smooth muscle begins to associate


Describe the structure of a vein

- Larger diameter, thinner wall
- More connective tissue
- Fewer elastic and muscle fibres


Describe the layers of small/medium veins

- Thin tunica intima
- Thin tunica media
- Well developed tunica adventitia


Describe the layers of large veins

- Thicker tunica intima
- Less prominent tunica media
- Well developed Adventitia


What are venae comitantes?

Deep paired veins that accompany arteries


Describe how venae comitantes function

- Artery pulses

- Causes venous return in adjacent veins


What is the pathway of blood from the heart to the capillaries?

- Heart
- Large (elastic/conducting) arteries
- Medium (muscular/distributing) arteries
- Arterioles
- Metarterioles
- Capillaries


Describe continuous capillaries. Where can they be found?

- Cells are joined by tight junctions
- Most common (nervous, muscle and connective tissues etc)


Describe fenestrated capillaries. Where can they be found?

- Disruptions on thin parts of endothelium bridged by a thin diaphragm (except renal glomerulus)
- Gut, endocrine glands and renal glomerulus

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