Capillaries and Lymphatics Flashcards
Why do we have the cardiovas system?
For exchange
What are capillaries?
Site of exchange between blood and tissues
Features of capillaries
-Very thin walls for efficient exchange
-Large CSA for more exchange
-Unlike the pulsatile flow of the heart, caps have smooth flow
Why not thick walls?
They act more as a barrier
What are cap cells?
Single endothelial cells that form a tube
What does RBC fill up most of?
The lumen of the cap
size of RBC
8-10 µm in diameter
How does the RBC exchange in the cap
They are so big that they press up hard against the cap wall, making the distance for exchange as small as possible
How does endo cell form cap
The Cyto wraps around and connects through a tight junction
What determines how leaky a cap is?
How many tight junctions are present
Structures through which the blood flows in a cap
The terminal arteriole –> the side branches etc –> the postcapillary venule
What does more flow through the cap branches mean?
More heat exchange
What are precap sphincters
Can constrict/relax to control the flow of blood
How does the precap sphincters send blood to just the venule
Through the matarteriole and thoroughfare channel to the venule by constricting blood flow to the other branches. Aka vascular shunt
Metarteriole and thoroughfare channel together are called
The vascular shunt
3 types of caps + short def
- Continuous: most common, have tight junctions, the default, forms a continuous cellular barrier and things must go through endo cell
- Fenestrated: somewhat leaky, things dont have to go through cyto
- Sinusoidal: very leaky, very large openings
Last two are for very specific functions only
How do you make a cap more leaky?
By changing the structure of the endo cell
What are the dots in the cyto of continuous endo cell?
Vesicles that pick stuff from apical side and transports to basal side and vice versa, active process for cellular exchange for stuff that cannot diffuse passively
Can gases diffuse passively
Yes
Can stuff go through tight junction
yes, depends how leaky
What is the thin fuzzy layer
ECM, fuzzy collagen that is connective tissue that acts as an anchor for endothelium tube
What do fenestrated caps have?
More porous openings, making it easier to pass through
Structure of fenestrated
Thicker parts of endo where nucleus is
- Basement mem that stuff has to pass through
- Fenestrations, floating dots of cyto, stuff passes in between the gaps
Size of sinusoidal caps
30-40µm
What is incomplete in sinusoidal
The basement layer
Structures of sinunoidal
- Smooth endo bits
- Fenestrations
- Larger holes with incomplete basement but holes not large enough to let the RBCs pass through
Example of liver cell
Areas that have large holes dont have basement, so liver cells have direct contact with rich intestinal fluid + toxins
What do the lymph nodes do?
Where the lymph goes to be surveyed for foreign antigens
Functions of the lymphatic system
- Drains excess tissue fluid & plasma proteins from
tissues and returns them the blood vas volume - Filters foreign material from the lymph.
- ‘Screens lymph for foreign antigens & responds by
releasing antibodies & activated immune cells. - Absorbs fat from intestine (gut mucosa) and transports to blood as difficult to absorb these through caps
Structure of lymphatic system
- Made of endo cells, finger-like projections
- Commence as large, blind ending capillaries.
- From small intestine (under gut mucosa), a special group of lymphatic vessels called lacteals drain fat-laden lymph into a collecting vessel called the cisterna chyli.
- Larger (thin wall) collecting vessels have numerous
valves to prevent backflow due to low P flow
- Commence as large, blind ending capillaries.
Another name for Cisterna chyli
Milk jug as it noticeable and drains fat rich lymph after a fat rich meal
Why do tissues become swollen?
If the lymph cannot drain fluid that has entered the tissues quick enough
What drains into the blood vas system through the left subclav vein
Lymphatic collecting vessels on the left side of face, chest and below diaphragm, collect in the thoracic duct and to left subclav (valves at thoracic to prevent backflow)
What drains into the right subclav
Lymphatic collecting vessels on the right side of face, chest
Where is the Cisterna Chyli?
Next to the Aorta
Most common places for nodes
Cerical, inguinal, groin, Axillary
Structure of a lymph node
Strands running through it, attatched are immune cells.
Lymph runs through the afferent, bathes immune cells to detect foreign pathogen and leaves through efferent and the drain back into blood vas system
Why is breast cancer dangerous?
Cancer cells in the breast can drain into the lymphatics of breast tissue –> up the axillary lumph nodes –> righ lymphatic duct and into the blood vas system through the right subclav vein and metastasise
How do we know if cancer has metastasises?
Dye to check if proliferation in lymph, if yes then patient given chemo to treat for possibility of metastasised cancer
