Lecture 7 - Capillaries & Lymphatics Flashcards
Capillaries
site of exchange between blood and tissues
Capillaries function demands
- very thin walls
- large cross sectional area of capillary bed. (much slower blood flow)
- slow & smooth blood flow
Capillary structure 3 types
Continuous (most widespread)
Fenestrated (leaky)
Sinusoidal (very leaky)
The structure of capillaries varies according to
rate of exchange needed, and how controlled the
exchange must be.
Continuous capillary (diametre)
8-10μm
Skeletal & cardiac muscle
Fenestrated capillary (diametre, found where)
8-10μm
Glomerulus, Kidney, small intestine.
Sinusoidal capillary (diametre, found where)
30-40μm diameter
Liver sinusoids
continuous (movement of substances)
Lipid soluble substances (diffusion through membrane)
Water soluble substances (through intercellular clefts)
Large substances (via vesicles or caveolae)
Sinusoidal and fenestrated (movement of substances)
difference between continuous.
Water soluble substances (through fenestrations & intercellular clefts)
Lipid soluble substances (diffusion through membrane)
Large substances (via vesicles or caveolae)
Lymph vascular system
An open entry drainage system
porous blind ending capillaries
Lymph vascular system functions
Drains excess fluid and plasma proteins from tissue and returns them into the blood.
Filters foreign material from the lymph
Screen lymph for foreign antigens and responds by releasing antibodies and activated immune cells
Absorbs fat from intestine and transports to blood
Lymphatic vessels structure
Start as large, blind ending capillaries.
From small intestine, 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.
Lymph vessels
Thin walled
no RBCS (clear fluid)
Valves (2 leaflets)
Low pressure
Lacteals
Group of lymphatic vessels from small intestine
Drain fat laden lymph (fluid) into collecting vessel (cisterna chyli)
Cisterna chyli
Milk jug
Endothelial cells of lymph vascular system
Form flat like connections
Makes ends of the blind ending capillaries porous
Allows fluid to easily come between the endothelial cells and drain
Lymph valve
Face towards the heart
Back towards the body centre
Prevent backflow
Drainage of 2 body regions
Left side and below diaphragm
Right side of face neck, chest, upper limb.
Left side and below diaphragm
Lymph drainage channels
Lymphatic collecting vessels (Drains through series)
Thoracic duct (drains back to lymph channel) joins with
Entrance of thoracic duct into left subclavian vein (left side of face and neck joins to single channel. Fluid drained. Close to right atrium.)
Right side of face neck, chest, upper limb.
Drains to
right subclavian vein
Cluster of lymph nodes
Cervical nodes
Axillary nodes
Inguinal nodes
Inguinal nodes
Groin
Axillary nodes
Armpit
Cervical nodes
Neck
Lymph nodes
Act as part of immune surveillance
Matrix of fibres that suspend a lot of immune cells (eg B cells sit and if encounter antigen they’ll become activated and produce antibodies against foreign antigen)
afferent lymphatics
Bring lymph from periphery drains through lymph nodes
Efferent lymphatics
Takes lymph and find a subclavian vein and drain into the blood vascular system.
