Basics
This system consists of arteries, capillaries, and veins. General functions: to transport blood throughout the body and return it through the heart via blood vessels and the tissues of those vessels contribute to the maintenance of blood pressure.
The Vascular System
Capillaries main function?
Their walls are one cell thick and composed of ____ ____ epithelium. This permits exchanges between blood and tissue fluid.
Function: carry blood from arterioles to venules.
Simple Squamous
What are the 3 major pathways of circulation?
What is the pathway before birth that includes the placenta?
Pulmonary, Systemic, Hepatic portal
Fetal circulation
Blood Pressure is defined as the force exerted by the blood against the walls of blood vessels and is measured in mm HG.
Systolic pressure occurs during ventricular _____. Diastolic pressure occurs during ventricular _____.
Normal Range of systemic arterial BP?
Systolic/contraction Diastolic/relaxation
90 to 120/60-80 mm Hg.
Why is slow flow in the capillaries important?
To permit sufficient time for exchange of gases, nutrients, and wastes.
These vessels carry blood from the heart to capillaries and have 3 layers (Inner, Middle, Outer) in their walls. Name 1: the vessel type, 2: the proper name for each wall layer, and 3: its function.
1: Arteries. 2 & 3: Inner (tunica intima)-Prevents abnormal clotting, produces chemical to control BP. Middle (tunica media) Control BP with constriction or dilation. Outer Layer (tunica externa) prevents rupture of vessel.
These are very permeable capillaries found in the liver, spleen, pituitary gland, and red bone marrow- Their permeability permits proteins and blood cells to enter or leave the blood.
Sinusoids
Right Ventricle > Pulmonary artery > Right and Left pulmonary arteries > Pulmonary capillaries > Pulmonary Veins > Left atrium
In the Pulmonary Circulation Pathway-(shown above) where does gas exchange take place and by what process does the exchange happen?
Gas Exchange happens in the pulmonary capillaries.
The process of exchange is diffusion.
Outside of the arteries, BP gets lower. Within the _____, BP on arterial side is 30 to 35 and 12 to 15 on the venous end- to allow for filtration but prevent rupture. BP decreases more in veins, approaching zero in caval veins.
Pulmonary BP is always low- the right ventricle wall is thinner and it pumps with less force( about 1/6 the force of left). Why is this important in regard to lung function?
-capillaries
-Low BP prevents filtration and accumulation of tissue fluid in the alveoli.
Normal range for pulmonary BP?
Remember, it's always low to exert less force and prevent filtration, so tissue fluid does not build up in the alveoli.
20 to 25/8 to 10 mmHg
These vessels carry blood from the capillaries to the heart and have 3 layers (Inner, Middle, Outer) in their walls. Name 1: the vessel type, 2: the wall layer and how it is different from the other main type of vessel
1: Veins 2 & 3: Inner- Folded into valves/prevents backflow of blood. Middle- Thinner than arteries, less smooth muscle b/c it does not control BP. Outer- Thinner than arteries, less fibrous connective tissue b/c it has a higher capacity than arteries.
Theses smooth muscle cells at the beginning of each capillary network regulate blood flow into the capillary networks on the basis of tissue needs. Dilate in active tissue, constrict in less active tissue.
Precapillary sphincters
_____ > Aorta > Systemic arteries > Capillaries in body tissue > Systemic Veins > Superior and Inferior caval veins > ______
Name the starting and ending point (Both within the heart) for Systemic Circulation.
Left Ventricle/Right Atrium
(For a better look at systemic arteries and systemic veins, look at pages 300-301)
The Maintenance of Systemic BP is complex with many mechanisms and factors that contribute. Name the 7 physiological factors and processes that interact to keep BP within normal limits.
Venous Return, Heart Rate and Force, Peripheral Resistance, Elasticity of the large arteries, Viscosity of the blood, Loss of blood, Hormones.
Describe the movement of Oxygen and CO2 in Pulmonary circulation within the lungs.
Oxygen moves from the air in the alveoli to the blood in the pulmonary capillaries. CO2 moves from the blood in the pulmonary capillaries to the air in the alveoli.
This is a connection between vessels of the same type. Ex: Vein to vein, artery to artery.
Their general function is to provide alternate pathways for blood flow if a vessel is blocked.
Anastomoses.
Arterial anastomoses ensure blood reaches capillaries. Venous anastomoses ensure blood is able to return to the heart.
Name the parts/tissues without capillaries.
Epidermis, cartilage, lens and cornea of the eye.
Hepatic portal circulation-is a subdivision of systemic circulation and takes blood from the digestive organs and spleen > Portal Vein> through the liver> back to the heart.
What is the purpose of the blood going through the liver?
This enables the liver to modify blood from those organs before returning to the heart.
Examples- removes excess glucose, detoxifies alcohol and other potential poisons, stores and changes some nutrients, bilirubin from the spleen is secreted into bile.
Metabolically active tissues require more oxygen and receive a greater proportion of circulating blood (blood flow to these tissues or organs increases by dilation of precapillary sphincters) Less active tissues, blood flow is decreased temporarily (constrictions of precap sphincters and arterioles) Example- During Exercise- the heart, lungs, and skin need more blood and 02 as cardiac output increases; Digestive system, Kidneys, bones- get less blood flow and can function adequately. This entire process is referred to as what?
Distribution of Blood Flow
Concerning the maintenance of systemic BP-
Venous return maintenance when the body is vertical is aided by constriction of veins with the valves preventing back flow of blood and what 2 pumps?
Skeletal muscle pump and Respiratory pump
Specific name for the smaller arteries?
Specific name for the smaller veins?
- Arterioles
-Venules
Name how these capillary exchanges happen ( the process used)
Oxygen and Carbon dioxide?
Nutrients and formation of tissue fluid?
The pull of waste products and tissue fluid into capillaries?
O2 and CO2 - exchanged by diffusion.
Nutrients/tissue fluid- Filtration created by BP
Waste/tissue fluid-Albumin in blood creates Colloid Osmotic pressure (a pulling pressure that pulls in waste- the return of tissue fluid maintains blood pressure and volume)
The Fetus depends on the mother for provision of oxygen/nutrients and removal of waste products within circulation. What is the site of exchange between fetus and mother?
Excluding Umbilical arteries and vein- what 3 structures used in fetal circulation become nonfunctional after birth, when lungs expand and pulmonary circulation begins?
Placenta
Ductus venosus(takes blood from umbilical vein to fetal inferior vena cave)
Ductus arteriosus (takes blood from pulmonary artery to aorta, bypassing fetal lungs)
Foramen ovale (permits blood flow from right to left atrium to bypass fetal lungs)
The mechanisms that regulate systemic BP can be divided into 2 types. Name them and give an example of each.
Intrinsic Mechanisms- Heart (venous return increases, ventricles pump more forcefully-BP increases) Kidneys- Decreased blood flow, decreases filtration (less urinary output preserves blood volume)
Nervous Mechanisms- involving medulla (vasomotor center) and autonomic nervous system- Heart and Peripheral resistance- (see pg 315 for a flow chart)
The speed with which blood flows throughout parts of the vascular system is called its what?
It is inversely related to the cross sectional area of the particular segment of the vascular system (meaning when one goes up, the other goes down) Which part of the vascular system has the largest cross sectional area? Which has the lowest?
Based on your answers above, which area has the slowest velocity blood flow?
-Velocity
Largest- Capillaries Lowest-Aorta
Slowest Velocity- Capillaries