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Chapter 21
Vessels
Term | Definition |
---|---|
Vessels | heart and blood vessels form a closed-loop system blood constantly pumped to and from tissues vessels can pulsate and change shape according with bodys needs |
Blood Vessels | share names with body region systemic=body (extend to & from body tissues) pulmonary=lungs (blood to lungs for gas exchange) |
3 types of blood vessels | Arteries (carry blood away) Veins (carry blood to heart) Capillaries (connection between smallest arteries and veins) Nutrients, waste, and gases exchange |
Artery | thick, elastic wall, small lumen must withstand forceful cardiac contractions resilient & strong; largest closest to heart, smallest further away |
Vein | thin wall, large lumen, valves stretchable; not subjected to high pressure small at beginning and large towards the heart |
Capillary | single cell wall |
Blood vessel layers are tunics | Tunica Intima (innermost) simple squamous, produces vasoconstrictors and vasodilators( chem.) Tunica Media (middle ) smooth muscle; thickest layer; allows changes in diameter Tunica Externa (outer) Strong; flexible thickest in veins; thin in arteries |
Aneurysm | weakened arterial wall MC cause in atherosclerosis + high blood pressure MC sites are aorta, renal arteries, circle of Willis at base of brain Pain/ death due to pressure in surrounding nerves, tissues, & organs |
Conducting & Disturbing Arteries | Conducting(largest, closest to heart, Elastic) Aorta, Carotid, & Subclavian Disturbing(median size, Most Common) Brachial, femoral, & renal |
Arterioles | Smallest arteries, resistance vessels cuz of flow resistant using smooth muscle contractions help regulate blood pressure & control how much blood enters an organ connected to capillaries(metarterioles) |
Venules & Medium-sized Veins | smallest veins, collect blood from capillaries, thin walls, porous; can exchange fluid with surrounding tissues venules converge, have thicker and more elastic walls one-way flow to prevent backflow & help fight gravity in legs |
large veins | formed medium size veins converge on the heart thick tunica externa |
Cappilaries for Exchange | microscopic vessels connecting arterioles & venules site of gas, hormone, and waste exchange small diameter- one cell at a time (4-6 cell width) |
Capillary Organization into beds | network connectings microcirculation |
precapillary Sphincter | 'beaver dam' band of smooth muscle that adjusts blood flow during exercise(+ oxygen) OPEN during rest(-oxygen)CLOSE allows blood to bypass the network & head straight to venule on the throughfare channel |
3 types of capillaries | Continuous (uninterrupted lining; only allows small molecules) Fenestrated (tiny windows in the endothelial lining; small molecules & limited amounts of protein) Sinusoid (open-pore capillaries with increased permeability; allows RBCs, WBCs, serum |
Capillary Exchange | moving oxygen, glucose, hormones, and nutrients out taking up waste gases & substances needing transport to other parts of body Glucose=liver, Calcium=bones, antibodies=immune cells, hormones=endocrine glands |
3 mechanisms of capillary exchange | diffusion=gases only filtration=hydrostic pressure(heartbeat) osmosis=osmotic pressure(water to salt) |
Edema | fluid filters out of capillaries faster than it can be absorbed and builds up in tissues 3 causes: increased capillary filtration, reduced capillary reabsorption, & obstructed lymphatic drainage |
Portal Systems | when blood flows through two networks (capillaries) than one as usual 2 major circulation pathways: somatic & Pulmonary |