"NeuroVerse: Unraveling the Mysteries of Nervous Tissue",NEUROSCIENCES anatomy,2nd year,DUHS,class notes
Hemopoiesis
Connective Tissues
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The Circulatory System
Circulatory System Overview:
o The circulatory system directs blood cells and substances throughout the body.
o It comprises the blood vascular system and the lymphatic vascular system.
Blood Vascular System (Cardiovascular System):
o The heart pumps blood through the system.
o Arteries carry blood away from the heart to various organs, decreasing in size as they branch.
o Capillaries, the smallest vessels, facilitate the exchange of oxygen, carbon dioxide, nutrients, and
waste products between blood and tissues. They form microvasculature
o Veins gather blood from venules and gradually enlarge as they approach the heart, transporting
blood back to be pumped again.
o Divided into pulmonary circulation (oxygenation in the lungs) and systemic circulation (nutrient
delivery and waste removal in body tissues).
Lymphatic Vascular System:
o Begins with lymphatic capillaries, which merge into larger vessels.
o Thin walled and closed ended vessels that is filled with lymph. They merge forming larger
lymph vessels
o Largest lymph vessels connect with the blood vascular system, draining fluid from tissue spaces
back into the bloodstream.
Endothelium:
o The internal surface of all blood and lymphatic system components is lined with endothelium.
o Endothelial cells play crucial roles in maintaining a selectively permeable barrier, inhibiting clot
formation, regulating white blood cell migration, and secreting factors for vessel function and
growth.
HEART
o Heart Chambers and Function:
Cardiac muscle in the heart's four chambers contracts rhythmically to pump blood
through the circulatory system.
Right and left ventricles propel blood to the pulmonary and systemic circulation
Right and left atria receive blood from the body and pulmonary veins
o Heart Chamber Layers:
Endocardium:
Thin inner layer of endothelium and connective tissue.
Middle layer of smooth muscle fibers and connective tissue.
Deep subendocardial layer merging with myocardium, housing branches of the
heart's impulse-conducting system.
Myocardium:
, Thickest layer mainly consisting of spirally arranged cardiac muscle fibers.
Much thicker in ventricular walls, particularly the left ventricle.
Epicardium:
Simple squamous mesothelium supported by loose connective tissue.
Corresponds to the visceral layer of the pericardium.
Contains adipose tissue deposits for cushioning and produces lubricant fluid to
prevent friction within the pericardium.
o Cardiac Skeleton and Function:
Dense fibrous connective tissue forms part of the interventricular and interatrial septa,
surrounds heart valves, and extends into valve cusps and chordae tendineae.
Functions include anchoring and supporting heart valves, providing points of insertion for
cardiac muscle, and acting as electrical insulation between atria and ventricles.
o Impulse Conducting System:
Consists of specialized myocardial tissue nodes: sinoatrial (SA) node, atrioventricular
(AV) node, AV bundle (of His), Purkinje fibers
SA node initiates impulses, which propagate through atrial myocardium to stimulate
contraction.
AV node receives impulses and stimulates depolarization before passing them to the AV
bundle.
AV bundle bifurcates into left and right bundle branches, which further subdivide into
Purkinje fibers at the apex of the heart.
Purkinje fibers trigger simultaneous contraction of both ventricles.
o Neural Innervation:
Both parasympathetic and sympathetic neural components innervate the heart.
Ganglionic nerve cells and fibers near SA and AV nodes affect heart rate and rhythm.
Parasympathetic stimulation (vagus nerve) slows heartbeat, while sympathetic
stimulation accelerates pacemaker activity.
Afferent free nerve endings between myocardial fibers register pain
TISSUES OF THE VASCULAR WALL
Composition of Blood Vessel Walls:
Except for capillaries, all blood vessels contain smooth muscle and connective
tissue along with the endothelial lining.
The arrangement and amount of these tissues are influenced by mechanical
factors such as blood pressure and metabolic factors reflecting local tissue needs.
Endothelium Structure:
Specialized epithelium acting as a semipermeable barrier between blood and
interstitial tissue fluid.
Squamous, polygonal, and elongated endothelial cells with the long axis aligned
in the direction of blood flow.
Highly differentiated to mediate bidirectional exchange of molecules through
various mechanisms including diffusion, endocytosis, and transcytosis.
Functions of Endothelial Cells:
, Present a nonthrombogenic surface and secrete agents controlling clot formation.
Regulate local vascular tone and blood flow through secretion of vasoconstrictors
and vasodilators.
Play roles in inflammation and local immune responses by inducing white blood
cell migration and secreting factors affecting white blood cell activity.
Secrete growth factors promoting proliferation of white blood cell lineages and
cells comprising the vascular wall.
selectively permeable barrier, inhibiting clot formation, regulating white blood
cell migration, and secreting factors for vessel function and growth.
Smooth Muscle and Connective Tissue Components:
Smooth muscle fibers arranged helically in layers in vessels larger than
capillaries.
Arterioles and small arteries permit vasoconstriction and vasodilation due to more
gap junctions between smooth muscle cells.
Connective tissue components include collagen fibers, elastic fibers, and ground
substance components, varying based on local functional requirements.
Structure of Blood Vessel Walls:
Larger vessels have three concentric layers or tunics: intima, media, and
adventitia.
Intima consists of endothelium and a subendothelial layer.
Media comprises concentric layers of smooth muscle cells, elastic fibers, and
proteoglycans.
Adventitia is primarily composed of collagen and elastic fibers, continuous with
the organ stroma.
Vasa Vasorum and Vasomotor Nerves:
Larger vessels have vasa vasorum (arterioles, capillaries, and venules) in the
adventitia and outer part of the media to supply nutrients to thicker vessel walls.
Adventitia contains a network of unmyelinated autonomic nerve fibers
(vasomotor nerves) releasing norepinephrine, more densely innervating arteries
than veins.
VASCULATURE
Elastic Arteries:
Includes aorta, pulmonary artery
Also known as conducting arteries.
Well-developed tunica intima and internal elastic lamina. Has endothelium
and connective tissue with smooth muscle
Thick tunica media with elastic lamellae alternating with smooth muscle
layers.
Thin adventitia with vasa vasorum has Connective tissue
, Arterial Sensory Structures:
Carotid sinuses act as baroreceptors monitoring arterial blood pressure.
Carotid bodies and aortic bodies contain chemoreceptors monitoring blood
CO2 and O2 levels. Chemoreceptors contribute to autonomic nervous
system regulation.
Muscular Arteries:
Distribute blood to organs and regulate blood pressure by vaso
constriction and dialation
Intima has endothelium and connective tissue with smooth muslce and
interal elastic lamina. Thin subendothelial layer
Thinner tunica media, with up to 40 layers of smooth muscle cells and
elastic lamellae.
Adventita has connective tissue with vasa varorum sometimes
Presence of an external elastic lamina in larger muscular arteries.
Arterioles:
Branch from muscular arteries and form microvasculature. Smallest
arteries. Resist and control blood flow to capillaries. Imortant in systemic
blood pressure
Intima has endothelium. Has no connective tissue or smooth muslce. Has
Thin subendothelial layer, absent elastic laminae
Media has 1-3 layers of smooth muscle
Adventita: inconspicuous adventitia, very thin connective tissue layer
Act as major determinants of systemic blood pressure.
Can have specialized functions such as thermoregulation or participation
in venous portal systems.
Specialized Microvascular Pathways:
Arteriovenous shunts allow direct connection between arterioles and
venules, important for thermoregulation.
Venous portal systems involve blood flowing through two successive
capillary beds separated by a portal vein, efficient for delivering hormones
or nutrients to specific tissues before returning to the heart.
Capillary
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