Unit 1 - Cardiovascular/Circulatory System
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Structure and Function of: Blood Vessels (BV's).
- Form a closed system of tubes.
- 1.) Carry blood away from the heart
- 2.) Transport it to the tissues of the body
- 3.) Return it to the heart.
Structure and Function of: Arteries
- The Wall of an Artery Consists of:
- 1.) A tunica interna
- 2.) A tunica media (Maintains elasticity and contractility)
- 3.) A tunic externa
- 1.) Carry blood away from the heart to the tissues.
- 2.) Functional Properties of Arteries:
- a.) Elasticity
- b.) Contractility
- 3.) Two Types of Arteries:
- a.) Elastic
- b.) Muscular
Functional Properties of Arteries: Elasticity and Contractility.
- 1) Elastic tissues in tunica interna & media allow arteries to accept blood under great pressure from the contraction of the ventricles
- 2.) Systemically sends blood .
- 1.) Smooth muscle in the tunica interna & media allow arteries to ↑ or ↓ lumen size.
- 2.) Limits bleeding from wounds.
Structure and Function of: Elastic Arteries (Conducting Arteries)
- Large arteries with more ↑ fibers and ↓ smooth muscle.
- 1.) Pressure reservoir.
- 2.) Receive blood under pressure, propel it onward.
- 3.) Called "Conducting" b/c they conduct blood from the heart → medium sized muscular arteries.
Structure and Function of: Muscular Arteries
- Have ↑ amount of smooth muscle in their walls.
- Distribute blood to various parts of the body.
Structure and Function of: Arterioles
- Very small (almost microscopic) arteries that deliver blood → capillaries
- 1.) Vasoconstrict (↓ BV lumen size) and vasodilate (↑ BV lumen size).
- 2.) ∴ key role = Regulating blood flow from arteries → capillaries
- 3.) Alter arterial BP.
Structure and Function of: Capillaries
- Structure1.) Microscopic vessels that usually connect arterioles & venules.
- 2.) Only a single layer of cells (endothelium) and a basement mbn.
- 3.) Blood flow → cap's = regulated by vessels w/ smooth muscle in their walls.
- 4.) Precap. Sphincters = Rings of smooth muscle fibers (cells)
- Function1.) Permit exchange of nutrients & wastes ↔ the blood & tissue cells via interstitial fluid
- 2.) Precap. sphinc. regulate blood flow → true cap's.
- 1.) Microcirculation = Blood flow via the capillaries
- 2.) Near ~every cell in body, but distrib. varies w/ metab. act. of the tissue
- 3.) Branch to form extensive cap. network thr/out the tissue.
- a.) Network ↑'s surface area → allows rapid exch. of large quantities of materials.
- Types of Cap's:
- 1.) Continuous
- 2.) Fenestrated
- 3.) Sinusoids
Structure and Function of: Venules
- 1.) Small vessels formed from union of several cap's.
- 2.) Ven's merge to form veins.
- Drain blood from cap's → veins.
Structure and Function of: Veins
- Convey blood from the tissues → heart.
- 1.) Same 3 as arteries but thinner tunica interna & media, thicker tunica externa.
- 2.) Have ↓ elast. tiss. & smooth muscle.
- 3.) ∴ thinner-walled than art.'s.
- 4.) Contain valves to prevent backflow of blood.
- Other Types1.) Vascular (venous) sinuses = Veins w/ very thin walls, no smooth muscle to alter their diam's.
- a.) (ie brain’s sup. sag. sinus & coronary sinus of the heart)
- 2.) Varicose veins caused by weak valves.
Structure and Function of: Anastomoses
- Union of branches of 2+ arteries supplying same region.
- Consist of 2 veins/a vein & an artery.
- Provide alt. routes for blood → tissue/organ.
- Other Types
- 1.) Collateral Circulation = Alt. flow of blood → a body part via ananastomosis.
- 2.) End Arteries = Art's that don't anastomose.
- a.)Occlusion of an End Artery = Interrupts blood supply to a whole organ segment → necrosis (death) segment.
Vasa Vasorum = ?
- Small BV's that supply blood to cells of walls of the arteries and veins.
At rest, where is the largest portion of blood?
In systemic veins & venules (Collectively = blood reservoirs).
Fxn of Blood Reservoirs
- 1.) Stores blood & (Via ven. vasocon.) can move blood → other parts of body if necessary.
- 2.) Hemorrhage (When BP & volume ↓) → vasocon. of veins in ven. reservoirs help compensate for blood loss.
- 3.) Principal Reservoirs = Veins of the abdominal organs (liver and spleen) & skin.
- 1.) Substances enter/leave cap's by diffusion, transcytosis, & bulk flow.
- a.) Simple Diffusion = Most important method of cap. exch.
- --Subst. (Like O2, CO2, Glucose, AA's, & Hormones) diffuse ↓ their conc. grad's.
- --All plasma solutes (Except larger proteins) pass freely → most cap. walls.
- -- BBB = Prime exception of diffusion of H2O-soluble materials → cap. walls.
- b.) Transcytosis = enclosing of subst's w/in tiny vesicles that enter cells by endocytosis.
- c.) Bulk Flow: Filtration and Reabsorption
- --Diffusion = ↑ important for solute exch. ↔ plasma & IF, Bulk Flow = ↑ important for reg. of relative volumes of blood and IF.
- --Balance of filtr. & reabsorp. ↔ IF & plasma = disrupted → allows abnormal ↑ IF (Edema)
Factors Affecting Blood Flow
- 1.) BP = Pressure on walls of a blood vessel (Clinical use: BP refers to press. in art's).
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