Microanatomy heart Flashcards
What is oedema?
Defintion
Types of oedema and its symptoms
An excessive accumulation of fluid in the interstitial fluid
- Extremely common presenting complaint or clinical sign
1. Pulmonary oedema: ankle swelling, breathlessness
2. Cerebral oedema: stroke
3. Peripheral Oedema
What is microcirculation?
Definition
What involves in microcirculation?
The microcirculation is the terminal vascular network of vessels smaller than 100 micrometers in diamter where the exchange of substances between the blood and the tissue occurs.
Arteriole
Metarteriole: vessel that brings blood do the venuos system
arterial venous malformation: where arteriole directly connects to the veins due to lack of capillaries
- in brain: with bleeding ro seizure
- in GI tract
True carpillary
Shunt vessel
venule
Muscular venule
Venule
Vein
Special characteristics of blood vessels
Capillaries
Arterioles
Capillaries: single layer of highly permeable endothelium
Arterioles: able to change their diameter by up to 50%-huge changes in flow
Functions of the microcirculation
6 points
- Oxygen transfer: occurs down a concentration gradient
- Regulation of water movement:balance between hydrostatic and oncotic pressures
- Transport of nutrients to tissues
- Removal of waste products
- Capacitance: venules contain a substantional amount of total blood volume
- Immune function: coordinates localised blood flow to inflamamation and changes permeability to permit migration of leukocytes
Types of capillary
What they are (3)
What they are composed of (4)
- Continuous capillaries
- Fenestrated capillaries
- Sinusoidal capillaries
Composed of:
- Endothelial cells held together by tight junctions
- Surrounded by a basement membrane
- No smooth muscle
Continous capillaries
Structure (3)
Function
Distribution (2)
Least permeable capillaries and most widely distributed
Structure: Sealed endothelium and tight junction
Sub divided into 2 further types:
1. Numerous vesicles (Caveolae)
2. Few vesicles (brain)
Pericyte
RBC
Endothelial cell
Pinocytotic vesicles
TIght junction
basement membrane
intercellular cleft: helps to move water
Function: Only peremable to small molecules such as resp gases and water
Distribution: Most widely distributed capillary
1. Lungs, skeletal muscle, skin
2. Brian (blood-brain-barrier)
Fenestrated capillaries
Structure
Function
Distribution
Structure: Small circular pores in the endothelial cells
Function: Relatively free passage of salts and water from the plasma to tissues
Distribution: found in tissues that are specialised for bulk transport
- kindeys, prancreas (plus other exocrine glands), GI tract
Sinusoidal/Discontinuous capillaries
Structure
Function
Distribution
Structure: wide spaces between endothelial cells
Allows RBC and WBC to pass through
Function: highest permeability
Distribution: found in the spleen and liver
Methods of solute exchange
4 methods and description
- Diffusion: Small molecules,gases,lipids and lipid soluble molecules can diffuse through the endothelial cell membrane
- Intracellular clefts: Water soluble molecules can move through intracellular clefts between the endothelial cells
- Fenestration: Large molecules (water-soluble) can move through the fenestrations
- Vesicles: Some protien and larger molecules can be transported in vesicles or caveolae
Diffusion
volume moved equation, what law it is
What factors affect the rate of diffusion
Determined by Fick’s Law
volume moved=surface area x concentration gradient x diffusion coefficient
- Surface area and diffusion distance: This depends on the density of the capilalries. If there is a high density then the surface area will be large and diffusion distance small
- Concentration gardient: The net rate of diffusion of a substance through any membrane is proportional to the concentration differences between the two sides of the membrane
Oxygen: concentration in plasma is greater than interstitial fluid so net movement is out of plasma. CO2 (reverse) - Diffusion coefficient: only small lipid molecules can cross the plasma membrane. These ahve a higher diffusion coefficient.
Extracellular Pathways
why these pathways are required
which vessel has this often and why
- lipid insoluble ions and larger molecules cannot easily cross the membrane
- passage is confined to intercellular clefts (water filled channels)
- Movement of these substances will depend on the permeability characteristics of the capillary
- in continous capilalries (e.g blood brain barrier)- passage of these molecules will be limited
- Capillaries with grater permeability (fenestrated capillaries) can facillitate the movement of larger lipid insoluble molecules
Caveolae
Specialise pits that undergo endocytosis
Fluid exchange
What the 2 forces are
How they detrmine fluid exchange
Starlings Forces: hydrostatic pressure and oncotic pressure (colloid osmotic)
Hydrostatic pressure: physical pressure exerted by either blood pressure or the interstitial fluid pressure
Oncotic pressure: gradient determined by the osmotic potential of the blood or interstitial fluid
Net flow of luid in/out of the vasculature is determined by the balacne of these two forces
Hydrostatic pressure
How it affects net filtration rate and why (arterial end and venous end)
At the beginning of the artery, fluid moves artery->cells because hydrostatic pressure of capilalries > hydrostatic pressure of interstitial fluid
Fluid comes back into the venous end because hydrostatic pressure is so low, so fluid doesnt move out
Oncotic pressure
How it affects net filtration rate and why (arterial end and venous end)
At the end of the venus, fluid moves cell-> artery because oncotic pressure of capillary > oncotic pressure of interstitial fluid
(most plasma protiens cannot leave the capillary, so higher concentration of plasma protein in capillary compared to interstitial fluid)
If oncotic pressure is the same, blood is filtered through your arterial because the hydrostatic pressure allows fluid to leave out of the capillary (arterial end)
