ANT 222 - SYSTEMIC HISTOLOGY

Between the arteries and the veins, we have capillaries. Capillaries are also referred to as
exchange vessels. The thin walls of capillaries allow 4 exchange of substances between walls
and
Each component of d CVS including d heart is structured into 3 layers;
1. Tunica Intima
2. Tunica Media
3. Tunica Adventitia
The tunica Media is made up of Endothelium which is continuous throughout d entire blood
vessels. It's a single cell layer of flattened epithelium (specifically simple squamous epithelium).
TheTunica Media is made up of smooth muscles which some degrees of variability depending
on the type of vessels

The tunica Adventitia is made up of connective tissues. The external layer

Th tunica Intima is d innermost layer.

This structural plan is same 2ru out d CVS with some variations.

The Heart
The Heart is a muscular organ that functions as a pump. It creates d force dat starts d
movement of Blood within d vessels.

The heart wall has three layers. The innermost layer is called the Endocardium which is usually
flattened Epithelial cells. The middle layer is called myocardium (Consists of cardiac muscles).

Characteristics of Cardiac muscle

The outer and third layer is called Epicardium. It's a layer of connective tissue that lies btw d
muscle and the neighboring pericardial cavity. From inside, d Epicardium is attached 2 d
myocardium
N/b; Divisions of the Pericardium
Pericardium

Visceral Pericardium Serous Pericardium

Parietal Pericardial Fibrous Pericardium

Serous fluid; 0.5

I'm some disease conditions, the serous fluid may Increase (Pericarditis) leading to reduced
cardiac output. Cause, the heart is not allowed to expand.

Heart Chambers
The heart is composed of left nd right atrial and ventricles. The atri lies superior 2 d ventricles
and d right and left atrial act as a receptacle 4 blood coming 4rm d body and lungs respectively.

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……
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The right side of d heart contains oxygen poor blood while the left side contains oxygen rich
blood. U der normal conditions and circumstances, blood 4rm d left side of d heart, does not mix
with blood 4rm d heart. D 2 sides R separated by Interatrial and Interventricular septa along d
midlines. There R 2 sets of valves located in d heart. D 1st set is called d Atrioventricular valves
which regulates one way movement of blood btw d atrium and d ventricles. D Atrioventricular
valve, consists of d mitral valve and d tricuspid valve. The mitral valve is located on d left side of
d heart while d tricuspid valve is located on d right. Dey form d one-way gateway between d
Atrium to the ventricles. The mitral has two cups while d tricuspid has three cusps. The other
sets of valves includes d pulmonary valve and d aortic valve. D pulmonary valve located btw d
right ventricle and d pulmonary artery on d right side. They control d ejection of blood
f…………..

The other sets is the aortic valve which is located on d left side of the heart btw d left ventricle
and d aorta. It allows, movement of blood from d left ventricle into d aorta. The action potential
responsible 4 cardiac contraction is generated in the sinoatrial node SA node. Located near d
orifice of d superior Vena Cava. D impulse is transmitted across d atrial nd 2 d Atrioventricular
node where it depolarizes d ventricles via d bundle of …….and associated………fibers.

The arteries and veins vary in there view and appearances although they have d same general
structure. Arteries have thicker and more …………….. arteries appear round and smaller in
diameter than veins because of d elasticity. Veins have thinner and less elastic walls and larger
diameter than Arteries.

In arteries, the tunica Media is d largest whereas in veins, the tunica externa is the largest. The
Endothelium of the Intima rests on a basement membrane.

In larger Arteries, Between d tunica Intima and tunica Media, there's a layer of elastic tissue
known as internal elastic membrane or internal elastic lamina. You only see this in larger
Arteries and never found in smaller arteries or vein of any calibar

Tunica Media; this layer varies with d type of vessels. It consists mainly of elastic tissues or
fibers. As you love away from d heart, d arteries become smaller and d level of elastic fibers
decrease and are replaced by …………….. this kayers in veins consists of mainly smooth
muscles. Also, in this layer, because of d presence of smooth muscles. This muscles R
controlled by ANS……………………………………
………………………………………………………………………………….

The tunica Adventitia, which is the outermost layer, consists of connective layer. This
connective tissue layer are attached 2 neighbouring
structure………………………………………… ………..

A table diff btw veins and arteries

Lymphatic System
What is a lymph?
The Lymph also called lymphatic fluid is a collection of the extra fluid that's drained from cells
and tissues (that is not reabsorbed into the capillaries) plus other substances.

Diff types of capillaries; Continuous Capillaries, Discontinuous Capillaries, Sinusoidal

The other substances Include proteins, fats, minerals, nutrients, damage cells, cancer cells and
foreign invaders such as virus etc. ……… …. …. …. …. …. ….. ..

Lymphs also transport infection fighting white blood cells (Lymphocytes)

Lymph Nodes
Lymph nodes are bean shaped glands that monitor and cleanse d lymph as it filters 2ru dem.
The nodes filter out dis damaged cells and cancer cells. This lymph nodes also store
Lymphocytes and other immune cells that attack and destroy bacteria and other harmful
substances in the fluid. There are about 600 Lymph nodes scattered 2ru out d body. Lymph
nodes may exist as si gle node or closely connected groups called chains. Examples are
location of lymph nodes include, armpit, groin, neck etc. Lymph nodes R connected 2 others by
lymphatic vessels

Lymphatic Vessels
These are d network of capillaries (Micro vessels) and a large network of tubes that's located
2ru out d body dat Transports lymphs away 4rm tissues.. Lymphatics vessels connect and filter
lymphs at d nodes as it continues 2 move 2wards a larger vessel called d collecting ducts. This
vessels operate very much like veins because dey work at a very low pressure. They have
series of valves in them 2 keep d fluid moving in one direction.

Collecting ducts

Lymphatic Vessels, empty their lymphs into d right lymphatic ducts and d thoracic ducts (also
known as d left lymphatic ducts). These ducts connects 2 d subclavian vein which returns
lymphs 2 d blood stream. D subclavian vein runs below d collar bone (The Clavicle). Returning
lymph 2 d blood stream helps 2 maintain normal blood pressure and volume. It helps prevents d
excess buildup of fluid around d tissue (Edema).

Other lymphoid organs include:

The …………………………………
2.
The thymus; This organ is located in d upper chest beneath d sternum. It matures a
specific type of white blood cells called d T Lymphocytes.
3. Tonsils and Adenoid: These Lymphoid organs, trap pathogens from d food nd air. They
are d bodies first line of defense against foreign invaders.
4. Bone Marrow: A soft spongy tissue in the center of certain bone such as d hip bone and
d breast bone. They R at d site of d production of
5. The Payers Patches: Small masses of lymphatic tissues in the mucus membrane that
lines the ……… intestine ………………………
6. Appendix: Contains lymphoid tissue that can destroy bacteria before it breaches the
intestine wall during absorption.

Lecture Two