Name the two main circulatory systems
Blood vascular system and lymphatic system
System of lymphatic vessels & nodes that
drain extracellular fluid from the tissues
back to the blood circulatory system after
passage through lymph nodes
System that absorbs lipids from the gut
The only artery that carries deoxygenated blood
The only vein that carries oxygenated blood
possess walls composed of three layers:
tunica intima (inner)
tunica media (middle)
tunica adventitia (outer)
Arteries and Veins
Epithelium type that lines ALL arteries and veins
Simple squamous epithelium
Composed of the lining Endothelial Cells, basal lamina & the associated subendothelial connective tissues
Tunica Intima (Inner)
Endocrine, exocrine, cell adhesion, clotting, anti-clotting & transport
Endothelial cell functions
Composed of fibroelastic connective tissue mixed with smooth muscle and often elastic laminae
(Internal & External Elastic Laminae)
Tunica Media (Middle)
Composed of fibroelastic connective tissue - inside it are small blood vessels
called the vasa vasorum & nerves that
send branches to supply the media
with blood & nerves
Tunica Adventitia (Outer)
Also called large arteries due to size &
conducting arteries because they conduct
the blood to the whole body, are subjected to high systolic pressures of 120-160 mmHg, & include the aorta & its major branches. It media is actually composed primarily of elastic fibers and laminae along with some smooth muscle.
Are also called distributing arteries because they distribute the blood from large elastic arteries to
various organs, include most of the named arteries of the human body, are medium-sized (smaller than elastic arteries but larger than
arterioles), are highly contractile WITH DISTINCT
SMOOTH MUSCLE LAYERS in the MEDIA
and with distinct internal and external elastic
Media is predominately smooth muscle
Muscular Artery (Media Trait)
Are unnamed, are the smallest arteries with
diameters averaging 0.1mm, the microvasculature starts at this level, NO ELASTIC LAMINA, functions include regulation of blood pressure!!!!!!!!!!!
Muscles surrounding the lumen contract and stop blood flow
arteriole blood pressure control
Narrow vessels that arise from arterioles. They give rise to capillaries which are surrounded by rings of smooth muscle cells (precapillary sphincters) at their origin. Constriction of precapillary sphincters keeps blood from entering capillary bed.
Smallest vessels of the blood circulatory system (5-10 µm) & form a complex, interlinking network
wall composed of a single layer of endothelial cells, a basal lamina & occasional contractile cells called pericytes, exhibit selective permeability, permitting exchange of O2, CO2, metabolites & other substances between blood & tissues. They are classified into 3 types, depending on the structure of their endothelial cells & the continuity of the basal lamina.
Continuous (somatic), Fenestrated (Visceral), and Sinusoid
3 Types of Capillaries
Lack fenestrae in their walls, contain numerous pinocytic vesicles, except in the CNS, have a continuous basal lamina.
Are located in nervous tissue, muscle,
connective tissue, exocrine glands & lungs.
Maintain strict control and are almost a "closed system."
Continuous (Somatic) Capillaries
Are formed of endothelial cells whose walls are
perforated with fenestrae, which allow more
diffusion from the lumen to tissues. These
openings are 60-80 nm in diameter & bridged by a diaphragm thinner than a cell membrane; in renal glomerulus the fenestrae are larger & lack a
diaphragm. They contain only a few pinocytic vesicles, have a continuous basal lamina, They are located in endocrine glands, the intestine, the
pancreas, & the glomeruli of the kidneys
AKA Discontinous Capillaries
Fenestrated (Visceral) Capillaries
Possess many fenestrae that lack diaphragms, have a diameter of 30-40 µm, which is much
larger than that of continuous & fenestrated
capillaries, lack pinocytic vesicles, have a discontinuous basal lamina. They are located in the liver, spleen, bone marrow, lymph nodes & adrenal cortex
They can contract and provide a mechanism for angiogenesis
Conduct blood away from the organs &
tissues to the heart, vary in size from less than 1mm to 4 cm diameter, have a larger lumen & a thinner wall and carry blood at low pressure, contain about 70% of the total blood volume at any given time, may have valves in their lumina that prevent retrograde flow of the blood, possess walls composed of three layers: tunica intima, tunica media & tunica adventitia
Include the vena cavae & pulmonary veins, possess smooth muscle in the tunica adventitia. Adventitia contains an extensive
vasa vasorum & nerves.
Partial oxygen pressure and osmotic pressure is lower in veins. This would lead to more vasa vasorum needed to supply the vessels sufficiently.
Why larger veins have a more extensive vasa vasorum
Include veins the size of the external jugular vein, have a diameter of 1-9 mm, some smooth muscle in media, adventitia is the DOMINANT layer
and is mostly CT
Small and Medium-Sized Veins
Are unnamed, have a diameter of 0.2-1mm, adventitia is dominant layer & has lots of collagenous ct, are involved in exchange of
metabolites with tissues & in diapedesis
A fold of endothelia with a core of fibroelastic connective tissue
Channels that connect two capillary or
venular systems, do not depend on the pumping action of the heart, uses sinusoidal capillaries, which are very "leaky" with discontinuous basal lamina
Consists of peripheral lymphatic capillaries, lymphatic vessels of gradually increasing size, &
lymphatic ducts. It collects excess tissue fluid (lymph) & returns it to the venous system and drains most tissues, except bone marrow & nervous system
Lymphatic Vascular System
Are thin-walled vessels that begin as blind-ended channels, are composed of a single layer of
attenuated endothelial cells that lack fenestrae & fascia occludens, are held open by small elastic filaments that also anchor them to the surrounding connective tissue, and possess a sparse or discontinuous basal lamina
Possess valves & are similar in structure to small veins, except that they have larger lumina & thinner walls. They have lymph nodes interposed along their routes that filter the lymph. Vessels converge & become two large trunks called the thoracic duct & right lymphatic duct that are similar in structure to large veins. Ducts empty into the junction of the internal jugular & subclavian veins.
Lymphatic Vessels and Ducts
A muscular pump with 4 chambers, 2 atria (receive blood) & 2 ventricles (pump blood to lungs or tissues). Enclosed in a pericardial sac composed of collagenous & elastic tissues. Has a central fibrous core & is made up of epicardial,
myocardial & endocardial layers. Has a impulse conduction system composed of muscle fibers modified for impulse conduction rather than
contraction. Receives sympathetic & parasympathetic nerve fibers that can modulate the rate of the heart beat, but do not initiate it. Produces atrial natriuretic peptide, a hormone
secreted by atrial cells that increases loss of Na+,
PO4 & H2O by the kidneys -- decreases blood pressure
Serves as the lubricative outer covering of the heart and is a serous membrane including blood capillaries, lymph capillaries, and nerve fibers. It constitutes the visceral pericardium, is composed of simple squamous epithelium (mesothelium) on the external surface and a layer of fibroelastic connective tissue underneath it. It contains blood vessels for the heart wall, nerves, and adipose tissue.
Provides muscular contractions that eject blood from the heart chambers and made up of cardiac muscle tissue separated by connective tissues and includes blood capillaries, lymph capillaries, and nerve fibers.
The cardiac muscle cells are arranged end-to-end into tracts that tend to run in bundles & insert into the fibrous skeleton -- strands of
C.T. containing a rich vascular network lie between the tracts & bundles of cardiac muscle cells.
It is thinnest in atria & thickest in left
Serves as the protective inner lining of the heart chambers and valves, made of endothelial cells and a thick subendothelial layer of elastic and collagenous fibers.
Composed of an inner layer made of simple
squamous epithelium (endothelium) & a thin
layer of loose connective tissue.
It is thick in the atria and thin in the ventricles, is continuous with the intima of the blood vessels entering & leaving the heart, and the deepest layer (subendocardium) is composed of loose connective tissue that contains veins, nerves & Purkinje Fibers.
Consists of thick bundles of collagen fibers oriented in various directions. The main component is the central fibrous body located at
the level of the cardiac valves. Extensions of the central fibrous body surround the heart valves to form the valve rings. A downward extension of the fibrocollagenous tissue of the aortic valve ring forms a fibrous septum between the right and left ventricles called the membranous interventricular septum.
Fibrous Skeleton of the Heart
Blood is prevented from flowing back into the 2 ventricles at end of their contraction
Pulmonary and aortic valves
During heart contraction (systole), blood is prevented from flowing back into atria.
Right Atrioventricular (Tricuspid) Valve and Left Atrioventricular (Bicuspid) Valve
prevent regurgitation of valves
Chordae Tendinae (Bicuspid and Tricuspid)