Anatomy 2 - Blood Vessels, Blood Pressure and the Lymphatic System

What are the 3 principal categories of blood vessels?

Arteries - carry oxygenated blood away from the heart; veins - carry deoxygenated blood back to the heart; capillaries - connect arteries to veins to create a circuit

This is the simplest and most common route for blood

Heart > arteries > arterioles > capillaries > venules > veins

True or false; during one cycle, blood passes through only one network of capillaries

True

Walls of arteries and veins have 3 layers, what are they?

Tunica interna/intima (deep), tunica media (middle) and tunica externa (superficial)

This layer of the blood vessel wall is simple squamous epithelium and faces the lumen

Tunica interna/intima

What do endothelial cells produce when tissue around vessels are inflamed?

Cell-adhesion molecules

This layer of the blood vessel wall consists of smooth muscle and collagen

Tunica media

This layer of the blood vessel supports endothelium from rupturing and is for contraction

Tunica media

This layer of the blood vessel wall consists of smooth connective tissue

Tunica externa

What is vasa vasorum?

Small vessels that supply blood to outer part of the larger vessels

Describe the layering of a medium artery from most deep to most superficial

Endothelium, internal elastic lamina, tunica media, external elastic lamina and tunica externa

Describe the layering of a medium vein from most deep to most superficial

Tunica interna, tunica media and tunica externa

These are the biggest arteries; what are some examples?

Conducting (elastic or large) arteries. Examples: aorta, pulmonary trunk - blood from heart to lungs, common carotid - blood to the brain, subclavian - blood to upper limbs and common iliac arteries - blood to lower limbs

This artery delivers blood to specific arteries; what are some examples?

Distributing (muscular or medium) arteries. Examples: brachial - arm, femoral - legs, renal - kidneys and splenic arteries - spleen

These are the smallest of resistance arteries; what is their function?

Resistance (small) arteries - Arterioles. Function: Control the amount of blood to various organs; lumen is modulated with vasoconstriction and vasodilation

Which tunic is well developed in resistance arteries?

Tunica media

These are exchange vessels

Capillaries; where gasses, nutrients, wastes and hormones pass between the blood and tissue fluid

What are capillaries composed of?

Endothelium and basal lamina

What are the 3 capillary types from least permeable to most permeable?

Continuous, fenestrated and sinusoids

This is the least permeable type of capillary; what is it’s function?

Continuous capillary - very common, occurs in most tissues; it allows passage of solutes such as glucose

Where can you find fenestrated capillaries?

In organs that require rapid absorption or filtrations — such as the kidneys and small intestine; cells have filtration pores — fenestrations

This is the most permeable type of capillary; where are they found and what are there functions?

Sinusoids; found in the liver, bone marrow and spleen; they allow proteins and new blood cells to enter circulation

These have a greater capacity for blood containment than arteries

Veins; have a steady blood flow and low blood pressure

What are the 3 types of veins?

Postcapillary venules (smallest veins) - leukocytes leave the bloodstream though venule walls; medium veins - skeletal muscle pump propels venous blood back to the heart; large veins like vena cavae, pulmonary veins, internal jugular veins and renal veins

What is blood pressue?

The force that blood exerts against a vessel wall

Where is blood pressure measured?

Brachial artery

These are the two pressures recorded when taking blood pressue

Systolic (ventricular contraction) and diastolic (ventricular relaxation) pressure

What is the normal blood pressure for a young adult?

120/75 mm Hg - systole/diastole

This is the difference between systolic and diastolic pressue

Pulse pressure (systolic pressure - diastolic pressure)

BP is determined by these 3 variables

Cardiac output - how much blood is ejected into the arteries; blood volume - salt; resistance to flow - vasodilation and vasoconstriction

Besides the beating of the heart, this organ has the largest influence on blood pressure of any organ

The kidneys - excretes salt thus excreting volume

How does salt influence blood pressure?

Less salt = less volume so BP goes down; high salt = high volume so BP goes up

This is the opposition to flow that blood encounters in vessels away from the heart

Peripheral resistance

Resistance is determined by these 3 variables

Blood viscosity - albumin and RBCs raise viscosity the most; vessel length - longer = higher BP, shorter = lower BP; vessel radius - large lumen/hot = lower resistance, small lumen/cold = higher resistance

Albumin is produced by the _____

Liver

This is the most powerful influence on blood flow

Vessel radius; only significant way of controlling resistance

Define whether low and high viscosity speeds or slows the flow of blood

Low viscosity speeds the flow of blood; high viscosity slows the flow of blood

This is the rhythmic contraction and relaxation of vascular smooth muscle of arterioles

Vasomotion

What are the 3 ways of controlling vasomotor activity?

Local control, neural control and hormonal control

This is the ability of tissue to regulate their own blood supply

Autoregulation

Define the metabolic theory of autoregulation

If tissue is inadequately perfused, wastes accumulate, stimulating vasodilation which increases perfusion

These are substances secreted by platelets, endothelial cells and perivascular tissue to stimulate vasomotor responses

Vasoactive chemicals - vasomotor responses

What is shear stress? What does this stimulate?

The drag of blood flowing against the endothelial cells; stimulates endothelial cells to secrete vasodilators like nitric oxide

What is the vasomotor center and what does it do?

Medulla oblongata; it exerts sympathetic control over blood vessels throughout the body

These are the 3 autonomic reflexes of the vasomotor center

Baroreflexes, chemoreflexes and medullary ischemic reflex

This autonomic reflex responds to changes in blood pressure; what is able to detect this change?

Baroreflex; carotid sinuses detect increases in BP

What does an increase in BP lead to?

Inhibition of sympathetic cardiac and vasomotor neurons - leads to vasodilation and lower cardiac output; activation of the parasympathetic NS - slow heart rate and thus reduces BP

What does a decrease in BP lead to?

Activation of sympathetic cardiac and vasomotor neurons - leads to vasoconstriction and higher cardiac output; inhibition of the parasympathetic NS - increases heart rate and thus raises BP

This autonomic reflex responds to changes in blood chemistry

Chemoreflex

What are the 2 chemoreceptors?

Aortic bodies located in the aortic arch and carotid bodies located in the carotid arteries

What is the primary role of chemoreflexes?

To adjust respiration to changes in blood chemistry; stimulate breathing to eliminate CO2 and get more O2

What does hypoxemia (low O2), hypercapnia (high CO2) and acidosis stimulate? What does this increase?

Chemoreceptors to cause widespread vasoconstriction; increases BP and lung perfusion, leading to an increase gas exchange

This is the automatic response to a drop in perfusion of the brain

Medullary ischemic reflex; the medulla oblongata monitors its own blood supply

What is ischemia and what does it trigger?

Insufficient perfusion; triggers the medullary ischemic reflexes; increases heart rate and contraction force, causes widespread vasoconstriction and increases BP so that more oxygen will go to the brain

True or false; hormones also influence BP

True

This hormone raises BP and is a potent vasoconstrictor

Angiotensin II

This enzyme is required for the synthesis of Angiotensin II

Angiotensin-converting enzyme (ACE)

This hormone promotes Na+ retention by the kidneys and supports BP

Aldosterone

This hormone is secreted by the heart and lowers BP; how does it lower BP?

Natriuretic peptides; these peptides lower BP by inhibiting aldosterone which promotes vasodilation

This gland produces the antidiuretic hormone (prevents urination); what does this promote?

The posterior pituitary gland; promotes water retention and raises BP, it also acts as a vasoconstrictor

These are adrenal and sympathetic catecholamines

Epinephrine and norepinephrine; these cause vasoconstriction which raises BP

What are the two purposes of vasomotion (vasodilation and vasoconstriction)?

General control of BP; routing blood from one body region to another

What are the general functions of the lymphatic system?

Fluid recovery - fluids leaked from capillaries, 85% are reabsorbed; immunity - excess filtered fluid picks up foreign cells and chemicals from the tissues; lipid absorption - lacteals in small intestine absorb dietary lipids that are not absorbed by the capillaries

This is the recovered fluids of the lymphatic system

Lymph

These transport the lymph

Lymphatic vessels

What are lymphatic tissues composed of?

Aggregates of lymphocytes and macrophages

Describe lymphatic capillaries (terminal lymphatics)

Capillaries that are closed at one end, the endothelial cells overlap each other like roof shingles, this creates valve-like flaps that open when ECF pressure is high and close when its low

Where does lymph become blood?

In the lymphatic capillaries (terminal lymphatics)

These are an integral part of the lymphatic system; lymph passes through these to be filtered

Lymph nodes

What are the 2 collecting ducts of the lymphatic system?

Right lymphatic duct - empties into right subclavian vein; thoracic duct - empties into the left subclavian vein

Once lymph makes it to the subclavian vein, what does it beome?

Venus blood - deoxygenated blood

Name a factor of lymph flow

The more you move, the more lymph flow you get; lymphatic flow is one way; flows similar to those that govern venous return, except no pump like the heart

These are all lymphatic cells

Neutrophils - antibacterial; natural killer (NK) cells - large lymphocytes that kill anything foreign; T lymphocytes (T cells) - mature in the thymus; B lymphocytes (B cells) - antibodies that mature in bone; macrophages - antigen-presenting cells (APCs); dendritic cells - alert immune system; reticular cells - build lymphatic organs

This is the simplest form of lymphatic tissue

Diffuse lymphatic tissue - lymphocytes are scattered, not clustered; prevalent in body passages open to the exterior (respiratory, digestive, urinary and reproductive tracts); AKA mucosa-associated lymphatic tissue (MALT)

This lymphatic tissue is more structured and dense

Lymphatic nodules (follicles); dense masses of lymphocytes and macrophages; constant feature of lymph nodes, tonsils and appendix

These are the 2 primary lymphatic organs and where lymphocytes mature

Red bone marrow and thymus

These are the secondary lymphatic organs

Lymph nodes, tonsils and spleen; there is no maturation of lymphocytes here

What is red bone marrow involved in?

Hematopoiesis (blood formation) and immunity

This is a member of the endocrine, lymphatic and immune systems

The thymus - houses developing T lymphocytes (T cells)