M7: Blood vessel histology Flashcards
Functions of the circulatory system
- carry blood (obvi)
- exchange nutrients, waste and gases
- transport hormones, components of immune system, molecules for coagulation, enzymes, nutrients, gases, waste etc
- regulate blood pressure
- direct blood flow
types of blood vessels
ARTERIES
- ELASTIC (great vessels in heart)
- MUSCULAR (thick smooth muscle walls, route blood, maintain BP)
- ARTERIOLES (smallest level that leads into capillary beds)
CAPILLARIES
VEINS
thinner walls, less elastic tissues, less smooth muscle cells
- VENULES
- SMALL VEINS
- MEDIUM or LARGE VEINS
size of artery vs companion vein
veins have thinner wall, but diameter is larger than companion artery
blood vessel structure
in general, 3 layers:
- TUNICA INTIMA (or TUNICA INTERNA): inner layer, adjacent to lumen
- TUNICA MEDIA: middle layer, smooth muscle and elastic fibres
- TUNICA ADVENTITIA (or TUNICA EXTERNA): outer layer, adjacent to surrounding tissue
components of tunica intima
- Endothelium
- layer of simple squamous cells and basement membrane
- releases vasodilators
- LAMINA PROPRIA: thin connective tissue
- INTERNAL ELASTIC MEMBRANE (in arteries, not veins. has holes to allow things to move out to smooth muscle. gives elasticity)
*capillaries only have
components of tunica media
- Smooth muscle (2-40 layers)
- more in arteries, less in veins (1-2 layers)
- fibres circularly organized
- External elastic membrane (only present in arteries, have holes to allow movement of things in/out)
components of tunica adventitia/externa
- made of collagen and some elastic fibres
- gives strength to vessels
elastic artery structure function
aka conducting arteries
- largest arteries in body
- tunica interna: elastic, well-defined
- tunica media: thick, elastic fibre dominated, some smooth muscle
- tunica externa: thinner than media
- function: pressure reservoirs (elasticity allows big vessels to maintain pressure)
muscular artery structure function
aka distributing arteries
- medium diameter
- tunica interna: elastic, well-defined
- tunica media: thick, smooth muscles dominated, few elastic fibres
- tunica externa: thicker than media
- function: distribute blood to various parts of the body, arterioles
name for terminal end of the arteriole
metarteriole
bloodflow through capillaries
- arteriole
- metarteriole
- capillary bed
- most direct route is THOROUGHFARE CHANNEL
- PRECAPILLARY SPHINCTERS: muscles that can cut of flow to capillary bed and direct to thoroughfare channel
- postcapillary venule
- muscular venule
types of capillaries
CONTINUOUS
- no gaps between endothelial cells
- less permeable to large molecules
- e.g. muscle, nervous tissue
FENESTRATED
- have pores (fenestrae)
- highly permeable
- fenestrae are areas where cytoplasm is absent and plasma membrane is a thin porous daphragm
- e.g. intestinal villi, cilliary processes of eye, choroid plexus
SINUSOIDS
- large diameter with large fenestrae
- less basement membrane
- allow large molecules to cross into blood
- e.g. endocrine glands, liver, bone marrow
venule structure function
POSTCAPILLARY VENULES
- tunica interna: endothelium and basement membrane
- tunica media: none
- tunica externa: sparse
- function: drain capillary network, bloodflow into muscular venules
MUSCULAR VENULES
- tunica interna: endothelium and basement membrane
- tunica media: as diameter increases, smooth muscle increases
- tunica externa: sparse
- function: bloodflow into veins
vein structure function
- formed by union of several venules
- compared to arteries…
- thin tunica interna and media, thicker tunica externa
- less elastic tissue, more smooth muscle
- contain valves in all veins > 2mm diameter
- prevent backflow of blood
- folds in intima that overlapp
- more in lower extremities than upper
varicose veins
- dysfunctional valves in veins
- blood pools in veins
- causes: pregnancy, defective valves
- symptoms: swelling, pain, ulcers in ankle
