AP2 Exam 2 Flashcards
Blood composition:
40% blood cells (solid portion); RBC, WBC, PLTs
60% plasma (fluid portion): electrolytes (maintains osmolarity ~300mOsm/L) and proteins (albumins, globulins, fibrinogens)
Structure of arteries and veins (picture)
- Tunica externa aka adventitia: connective tissue, nervi vasorum, and vasa vasorum
- Tunica media: smooth muscle is innervated by SNS only
- arteries: external elastic lamina
- Tunica interna aka intima:
- arteries: internal elastic lamina
- veins: valves (more in lower limbs than upper) present
Tunics: Arteries vs. Veins (table)
Tunica interna/intima
Tunica media
Tunica externa/adventitia
The endothelium of the tunica interna/intima produces the following:
- Endothelin: vasoconstrictor
- Nitric oxide: vasodilator
- Prostacyclin: vasodilator; type of prostaglandin
- Thromboxane: vasoconstrictor
- tPA: promotes fibrinolysis
- vWF: promotes PLT aggregation
Additionally, the endothelium proliferates to form new cells during repair (angiogenesis)
Two types of arteries:
gradual transition from elastic to muscular (no clear demarcating line)
elastic (aka conducting arteries): highest % elastic fibers in tunica media; found closest to heart (aorta thru common carotid and iliacs; pressure reservoir [potential energy of the stretch])
muscular (aka distributing arteries): more muscle in tunica media (still some elastic recoil however relies on musculature to push blood fwd)= more vasodilation/constriction= adjust rate of flow; axillary, brachial, femorals
Anastomoses should only occur between ______ vessels.
like
*collateral circulation: results when blockage or flow slows in small vessels
Neovascularization:
vasculogenesis: occurs mostly in embryonic development; hemangioblasts proliferate
angiogenesis: new vessels from pre-existing vessels (new cap. from post cap. venules); triggered by hypoxia or damage
arteriogenesis: remodeling of existing vasculature>leads to collateral circulation; triggered by exercise or ischemic vascular disease
De novo means:
from the new
Arteriole structure:
aka resistance vessels
Tunica externa: very thin
Tunica media: 1-2 layers of smooth muscle; sympathetic vascular tone
Tunica intima: thin layer
Arterioles:
aka resistance vessels: resistance is due to blood components rubbing against the vessel wall
Metarteriole:
- short vessels that connect arterioles to the capillary networks
- structural characteristics of both an arteriole and capillary:
- arteriole-metarteriole junction: normal tunica media layer allowing for vasodilation/constriction
-
metarteriole-capillary junction: single circumferential smooth muscle cells that can acts as a sphincter (precapillary sphincter)
- thoroughfare channel: when precapillary sphincters are all closed, blood flows from arteriole>metarteriole>thoroughfare channel>venule
Capillaries:
aka exchange vessels; extensive number of cap. increase SA>rapid exchange of materials
exchange of nutrients and waste products can only occur at capillary post AND capillary venule level
very small: blood cells must slow down= buys time for exchange
capillary bed: arise from a single metarteriole
vasomotion: periodic relaxation/constriction of precap. sphincters (ensures blood flow at rest)
Types of capillaries:
- all cap. consists only of single endothelial layer and basement membrane (no tunica interna/externa)
- continuous:
- most common
- endothelium is continuous with small intercellular clefts (exchange of smaller molecules)
- CNS, lungs, muscle, skin
- fenestrated:
- many fenestrations (larger particles) and clefts
- kidneys, endocrine glands, villi of small intestine, choroid plexus, ciliary process of the eyes
- sinusoid:
- least common
- incomplete or absent basement membranes
- unusually, very large fenestrations and intercellular clefts
- may contain specialized cells (e.g. kupffer cells)
- liver, marrow, spleen, lymph nodes (lymph fluid), endocrine glands
Capillary portal systems:
blood passes from one capillary network into another capillary network
e.g. hypophyseal and hepatic portal systems (first pass)
Postcapillary venules:
allow for diapedesis (WBCs moving into tissues) due to porous nature
only other site of metabolic exchange
Muscular venules:
1-2 layers of smoother muscle
no metabolic exchange
most distensible elements of entire vascular system (reservoir for blood prn)
The thin walls of both ______ and ______ venules make them the most distensible elements of the entire vascular system.
postcapillary and muscular
serve as reservoirs of large amounts of blood prn
Veins have high capacitance: explain
capacity to distend to store high volume of blood
*lack internal and external elastic laminae= very inelastic
Most venous walls are ______ layers of smooth muscle with ______ amount of elastic and collagen fibers
thin
small
Low blood pressure in the veins allows blood to flow backwards (to a point): when?
during ventricular diastole
to a point: valves>cusps project into the lumen with the cup portion aiming toward the heart
Vascular sinus
vein with thin endothelial wall
no smooth muscle
dense connective tissue replaces tunica media and externa (provides support)
examples include: coronary sinus