Module 11: Blood Flow and Pressure

Aorta

The main artery that carries blood away from the heart to the rest of the body.

Pulmonary vein

Veins that carry oxygenated blood from the lungs to the left atrium of the heart.

Venae cavae

The two large veins (superior and inferior) that carry deoxygenated blood back to the heart.

Capillaries

Microscopic blood vessels where exchange of gases, nutrients, and wastes occurs between blood and tissues.

Arterioles

Small arteries that lead to capillary beds and control blood flow via vasodilation and vasoconstriction.

Blood viscosity

The stickiness of blood due to formed elements and plasma proteins affecting resistance.

Systolic pressure

The pressure exerted in the aorta during ventricular contraction.

Diastolic pressure

The lowest level of aortic pressure during ventricular relaxation.

Hypertension

Sustained elevated arterial pressure of 140/90 mm Hg or higher.

Hypotension

Low blood pressure below 90/60 mm Hg, possibly leading to inadequate blood flow to tissues.

Mean arterial pressure (MAP)

An average blood pressure in the system, calculated as the difference between systolic and diastolic pressure.

Compliance

The ability of blood vessels to stretch and accommodate varying volumes of blood.

Endothelial cells

Cells that line the blood vessels and play a key role in vascular function and exchange.

Autoregulation

The intrinsic ability of tissues to regulate their own blood flow according to their needs.

Fluid exchange

The process where fluid leaves capillaries at the arterial end and returns at the venous end, regulated by hydrostatic and osmotic pressures.

Transient elevations

Temporary increases in blood pressure due to changes in posture, emotions, or physical exertion.

Cardiac output (CO)

The volume of blood pumped by the heart per minute, calculated as heart rate multiplied by stroke volume.

Paracellular transport

Small molecules like ions, glucose, and water can navigate from the plasma to the ISF through this

Metarterioles

Small blood vessels that link arterioles to capillaries, helping regulate blood flow into capillary beds.

Precapillary sphincters

Smooth muscle fibers that regulate blood flow into capillary beds by contracting or relaxing.

Tight junctions

Connect endothelial cells in continuous capillaries (systemic)

Fenestrated capillaries

Endothelial cells contain pores (spaces between cells), more permeable than continuous capillaries, function in absorption or filtration

Continuous capillaries (systemic)

Tight junctions connect endothelial cells, some cleft allow for passage of fluids and small solutes

Sinusoid capillaries

Contain large diameter, fewer tight junctions and some fenestrations, found only in the liver, bone marrow, spleen, and adrenal medulla, can contain macrophages in lining to destroy bacteria

Vasoconstriction

The narrowing of blood vessels resulting from contraction of the muscular walls, which increases blood pressure.

Vasodilation

The widening of blood vessels resulting from relaxation of the muscular walls, which decreases blood pressure.

Lumen

Central blood-containing space, vessels vary in length, diameter, wall thickness, and tissue make-up

Venules

Formed when capillary beds unite. Very porous, allowing for fluid recycling

Veins

Thinner walls, larger lumens compared to arteries, low resistance. Contain the majority of blood volume. Have lowest blood pressure. Volume reservoir

Blood flow

Volume of flowing through he vessel, organ ,or entire circulation in a given period of time. mL/min

Blood pressure (hydrostatic pressure

Force per unit area exerted on wall of blood vessel by blood. mm Hg

Pressure gradient

Provides the driving force that keeps blood moving from higher to lower pressure areas. Depends systemically on the cardiac output.

Peripheral resistance

Opposition to flow, measuring the amount of friction blood encounters. With vessel walls

Total blood vessel length

The greater the vessel length, the greater the resistance

Vessel diameter

Represents the greatest influence on resistance

Laminar flow

A smooth, orderly flow of fluid in parallel layers with minimal disruption between them. Resistance free

Turbulent flow

An irregular and chaotic flow pattern characterized by eddies and swirls, leading to increased resistance and energy loss.

Vital signs

Pulse and blood pressure, along with respiratory rate and body temperature

Pulse

Pressure wave caused by expansion and recoil of arteries

Korotoff

Sounds heard through a stethoscope as blood pressure is measured, indicating the systolic and diastolic pressure.

Short term controls

Neural controls and hormonal controls

Velocity of blood flow

How fast the blood flows. Changes as blood travels through the systemic circuit. Fastest in the aorta, slowest in the capillaries

Autoregulation of tissue perfusion

Autonomic adjustment of blood flow to each tissue relative to its varying requirements

Two types of autoregulation (locally)

Metabolic controls and myogenic controls