Lecture 7: CIRCULATORY SYSTEM ANATOMY - PART 2 Flashcards
What is the function of capillaries?
Site of exchange between blood and tissues
What does the function of capillaries require?
Very thin walls, large total cross sectional area of capillary bed and slow and smooth blood flow
How does the total area of capillaries compare to arterioles?
Much larger which means much slower blood flow
What is found in a capillary?
Layer of endothelial cells, nucleus, red blood cells and intercellular (tight) junction
What is the size of a red blood cell?
8-10 micrometres
What is found in a capillary bed?
Terminal arteriole, precapillary sphincters, vascular shunt and post capillary venule
What is the terminal arteriole?
The end of the supply netwokk
What is included in the vascular shunt?
Metarteriole and thoroughfare channel
What is the post capillary venule?
Start of the drainage network
What are precapillary sphincters composed of?
Smooth muscle cells under involuntary control
What are precapillary sphincters able to do?
Constrict and prevent blood flowing into the capillary bed
What does the vascular shunt do?
Pushes blood straight from the supply to drainage without passing through the exchange network
What are the 3 types capillaries?
Continuous, fenestrated and sinusoidal
What are continuous capillaries?
Most widespread
What are fenestrated capillaries?
Leaky
What are sinusoidal capillaries?
Very leaky
What is the diameter of continuous capillaries?
8-10 micrometres (single file flow of RBC)
What is the most common form of capillary?
Continuous capillaries
What do continuous capillaries also have?
A surrounding basement layer of extracellular tissue produced by the endothelial cells which the substances must also pass through
what is the diameter of fenestrated capillaries?
8-10 micrometers (single file flow of RBC)
What do fenestrated capillaries have?
Porous openings called fenestrations
What is an example of fenestrated capillaries?
Glomerulus in the kidneys which filter the blood
What is the diameter of sinusoidal capillaries?
30-40 micrometres (multiple RBC flow)
What does the larger diameter of sinusoidal capillaries mean?
They are more likely to be involved in transport of nutrients and toxins rather than gases as RBC are further from the capillary wall
What are the size of the openings in sinusoidal capillaries?
Larger than fenestrations
How is the basement membrane in sinusoidal capillaries?
Incomplete
What is an example of sinusoidal capillaries?
Liver sinusoids
What are the methods of transport through capillaries?
Diffusion through membrane, movement through intercellular clefts, movement through fenestrations and transport via vesicles of caveolae
What substances diffuse through the membrane?
Lipid soluble substances
What substances move through intercellular clefts?
Water soluble substances
What substances move through fenestrations?
Water soluble substances
What substances move via vesicles or caveolae?
Large substances
How do substances move through continuous capillaries?
Diffusion through membrane, movement through intercellular clefts and transport via vesicles of caveolae
How do substances move through fenestrated and sinusoidal capillaries?
Diffusion through membrane, movement through intercellular clefts, movement through fenestrations and transport via vesicles of caveolae
What capillary doesn’t require transport through the basement membrane?
Sinusoidal
What is the lymph vascular system?
An open entry (drainage) system
What are the functions of the lymph vascular system?
Drain, filter, screen and absorb
What does the lymph vascular system drain?
Excess fluid and plasma proteins from tissues and returns them to the blood
What does the lymph vascular system filter?
Foreign material from the lymph
What does the lymph vascular system screen?
Lymph for foreign antigens and responds by releasing antibodies and activated immune cells
What does the lymph vascular system absorb?
Fat from intestine and transports it to blood
How does the lymphatic system commence?
As large, blind ending capillaries
What does the lymphatic system do from the small intestine?
A special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli
What do larger (thin wall) collecting vessels have?
Numerous valves to prevent backflow
How are lymph vessels described?
Thin walled (thinner than veins and arteries), no RBC’s and has valves
How is the body split when it comes to the lymphatic system?
The left side of the body and the right side of the body below the diaphragm are one section and the right side of the body above the diaphragm is another section
What does the lymph from the left side of the body and the right side of the body below the diaphragm do?
Enter the thoracic duct and drain into the left subclavian vein
What does the lymph from the right side of the body above the diaphragm do?
Enter the right lymphatic duct and drain into the right subclavian vein
What does the small intestine virus contain?
A lacteal which drains to the cisterna chill and then to the thoracic duct
Where are lymph nodes found?
Tend to be in clusters throughout the body but are also found separately
What are some of the nodes in the body?
cervical, axillary and inguinal
Where are cervical nodes?
In the neck
Where are axillary nodes?
In the armpit
Where are inguinal nodes?
In the groin
What is found in the structure of a lymph node?
Afferent lymphatics, efferent lymphatics and lymphoid cells
Where does the lymph enter lymph nodes?
Afferent lymphatics
Where does the lymph leave lymph nodes?
Efferent lymphatics
What does the lymph do in the lymph nodes?
Pass through a network of lymphoid cells which survey the fluid
Where does lymphatic drainage of the breast start?
Lymphatic vessels of the breast
What comes after lymphatic vessels of the breast?
Axillary lymph nodes
What comes after axillary lymph nodes?
Right lymphatic duct
What comes after right lymphatic duct?
Right subclavian vein
How can metastatic cancer occur in the breast?
Breast tissue lymphatic drainage can carry cancer cells into the blood vascular system
