Anatomy and Physiology

Blood and its composition

Blood

Blood is a fluid connective tissue. It circulates continually around the body, allowing constant communication between tissues distant from each other.

It transports:

oxygen from the lungs to the tissues, and carbon dioxide from the tissues to the lungs for excretion,
nutrients from the alimentary tract to the tissues, and cell wastes to the excretory organs, principally
the kidneys,
hormones secreted by endocrine glands to their target glands and tissues,
heat produced in active tissues to other less active tissues,
protective substances, e.g. antibodies, to areas of infection
clotting factors that coagulate blood, minimizing bleeding from ruptured blood vessels

Composition of Blood.

Blood is composed of a clear, straw-coloured, watery fluid called plasma in which several different types of blood cell are suspended. Plasma normally constitutes 55% of the volume of blood.
The remaining 45% is accounted for by the cellular fraction of blood. The two fractions of blood, blood cells and plasma, can be separated by centrifugation (spinning) or by gravity when blood is allowed to stand (See the picture below) Because the cells are heavier than plasma, they sink to the bottom of any sample.

Blood makes up about 7% of body weight (about 5.6 litres in a 70 kg man). This proportion is less in women and considerably greater in children, gradually decreasing until the adult level is reached.
Blood in the blood vessels is always in motion because of the pumping action of the heart. The continual flow maintains a fairly constant environment for body cells. Blood volume and the concentration of its many constituents are kept within narrow limits by homeostatic mechanisms.

Plasma

The constituents of plasma are water (90 to 92%) and dissolved and suspended substances, including:

plasma proteins
inorganic salts
nutrients, principally from digested foods
waste materials
hormones
gases.

Plasma proteins

Plasma proteins, which make up about 7% of plasma, are normally retained within the blood, because they are too big to escape through the capillary pores into the tissues. They are largely responsible for creating the osmotic pressure of blood, which keeps plasma fluid within the circulation. If plasma protein levels fall, because of either reduced production or loss from the blood vessels, osmotic pressure is also reduced, and fluid moves into the tissues (oedema) and body cavities.
Plasma viscosity (thickness) is due to plasma proteins, mainly albumin and fibrinogen. Plasma
proteins, with the exception of immunoglobulins, are formed in the liver.

Albumins

These are the most abundant plasma proteins (about 60% of total) and their main function is to maintain normal plasma osmotic pressure. Albumins also act as carrier molecules for free fatty acids, some drugs and steroid hormones.

Globulins

Their main functions are:

as antibodies (immunoglobulins), which are complex proteins produced by lymphocytes that play an important part in immunity. They bind to, and neutralize, foreign materials (antigens) such as microorganisms.
transportation of some hormones and mineral salts, e.g. thyroglobulin carries the hormone thyroxine and transferrin carries the mineral iron.
inhibition of some proteolytic enzymes, e.g. α2 macroglobulin inhibits trypsin activity.

Clotting factors

These are responsible for coagulation of blood . Serum is plasma from which clotting factors have been removed. The most abundant clotting factor is fibrinogen.

Electrolytes

These have a range of functions, including;

muscle contraction (e.g. Ca2+),
transmission of nerve
impulses (e.g. Ca2+and Na+),
maintenance of acid–base balance (e.g. phosphate, ).

The pH of blood is maintained between 7.35 and 7.45 (slightly alkaline) by an ongoing complicated series of chemical activities, involving buffering systems.

Nutrients

The products of digestion, e.g. glucose, amino acids, fatty acids and glycerol, are absorbed from the alimentary tract.

Together with mineral salts and vitamins they are used by body cells for

energy,
heat,
repair and replacement, and for the
synthesis of other blood components and body secretions.

Waste products
Urea, creatinine and uric acid are the waste products of protein metabolism. They are formed in the liver and carried in blood to the kidneys for excretion.

Hormones

These are chemical messengers synthesized by endocrine glands.

Hormones pass directly from the endocrine cells into the blood, which transports them to their target tissues and organs elsewhere in the body, where they influence cellular activity.

Gases

Oxygen, carbon dioxide and nitrogen are transported round the body dissolved in plasma. Oxygen and carbon dioxide are also transported in combination with haemoglobin in red blood cells .

Most oxygen is carried in combination with haemoglobin and most carbon dioxide as bicarbonate ions dissolved in plasma. Atmospheric nitrogen enters the body in the same way as other gases
and is present in plasma but it has no physiological function.

Cellular Contents of Blood

There are three types of blood cell .

erythrocytes (red blood cells)
platelets (thrombocytes)
leukocytes (white blood cells).

Blood cells are synthesized mainly in red bone marrow. Some lymphocytes, additionally, are produced in lymphoid tissue.

In the bone marrow, all blood cells originate from pluripotent stem cells (i.e. capable of developing into one of a number of cell types) and go through several developmental stages before entering the blood. Different types of blood cell follow separate lines of development. The process of blood cell formation is called haemopoiesis

Stages in the development of blood cells

Red Blood Cells

Red blood cells are biconcave discs; they have no nucleus, and their diameter is about 7.5 micrometres.

Their main function is in gas transport, mainly of oxygen, but they also carry
some carbon dioxide. Their characteristic shape is suited to their purpose; the biconcavity increases their surface area for gas exchange, and the thinness of the central portion allows fast entry and exit of gases. The cells are flexible so they can squeeze through narrow capillaries, and contain no
intracellular organelles, leaving more room for haemoglobin, the large pigmented protein responsible for gas transport.

Life span and function of erythrocytes

Erythrocytes or red blood cells are produced in red bone marrow, which is present in the ends of long bones and in flat and irregular bones. They pass through several stages of development before entering the blood.
Their life span in the circulation is about 120 days.
The process of development of red blood cells from stem cells takes about 7 days and is called erythropoiesis. The immature cells are released into the bloodstream as reticulocytes, and then mature into erythrocytes over a day or two within the circulation. During this time, they lose their nucleus and therefore become incapable of division

Both vitamin B12 and folic acid are required for red blood cell synthesis. They are absorbed in the intestines, although vitamin B12 must be bound to intrinsic factor to allow absorption to take place. Both vitamins are present in dairy products, meat and green vegetables. The liver usually contains substantial stores of vitamin B12, several years’ worth, but signs of folic acid deficiency appear within a few months.

Haemoglobin

Haemoglobin is a large, complex protein containing a globular protein (globin) and a pigmented iron containing complex called haem.

Each haemoglobin molecule contains four globin chains and four
haem units, each with one atom of iron . As each atom of iron can combine with an oxygen molecule, this means that a single haemoglobin molecule can carry up to four molecules of oxygen.
An average red blood cell carries about 280 million haemoglobin molecules, giving each cell a theoretical oxygen-carrying capacity of over a billion oxygen molecules.

Iron is carried in the bloodstream bound to its transport protein, transferrin, and stored in the liver. Normal red cell production requires a steady supply of iron. Iron absorption from the alimentary canal is very slow, even if the diet is rich in iron, meaning that iron deficiency can occur readily if
losses exceed intake.

Control of Erythropoiesis

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Terms used in Anatomy and Physiology

Terms commonly used in Anatomy will be understood after these abbreviations are understood since they will be used occasionally.

Ach: Acetylcholine
ACTH: Adrenal Cortico- trophic Hormone
ADH: Anti diuretic Hormone
ANS: Autonomic Nervous System
ATP: Adenosine Tri Phosphate
C: Cervical, cervical vertebrae, (i.e. C4 cervical vertebrae 4)
cm: Centimeter
CNS: Central Nervous System
CRH: Corticotropin Releasing Hormone
CSF: Cerebrospinal Fluid
DNA: Deoxyribonucleic Acid
/d: Per day
FSH: Follicular stimulating hormone
GHRH: Growth Hormone Releasing Hormone
GI: Gastro Intestinal
GnRH: Gonadotrophin Releasing Hormone
HCG: Human Chorionic Gonadotrophin hormone
Hcl: Hydrochloric acid

GH: Growth Hormone
ICSH: Interstitial Cell Stimulating Hormone
IGF: Insulin Growth Factors
IUD: Intra Uterine Device
L: Lumbar, lumbar vertebrae, ( i.e L3, lumbar vertebrae 3)
LH: Luteinizing Hormone
PNS: Peripheral Nervous System
PRH: Prolactin Releasing Hormone
PTH: Para Thyroid Hormone
RNA: Ribonucleic Acid
rRNA: Ribosomal Ribonucleic Acid
T: Thoracic, thoracic vertebrae, (T1 thoracic vertebrae 1)
T3: Triiodothyronine
T4: Thyroxin

Common Terms In Anatomy And Physiology

Anatomy: This is the study of structures that make up the body and how they relate with each other.

Physiology: This word is derived from a Greek word for study of nature. It is the study of how the body and its part work together or function.

Homeostasis: This is defined as how the composition of the internal environment is well controlled in a fairly constant state.

Atoms molecules and compounds: The smallest level of the body is in form of atoms.

Cell: A cell is the smallest independent units of life.

Tissue: A tissue is a collection of many similar or related cells that perform a specific function. The various tissues are grouped
into four groups. 1. Epithelial, 2. Connective, 3. Nervous and 4. Muscle tissue.

Organ: – This is a collection of two or more groups of tissues that works harmoniously together to perform specific function.

System: This ss a group of organs that work together to perform major function.

Anatomical Positions.

Anatomical positions are accepted universally as the starting points for positional references to the body. In anatomical positions, the subject(body of patient or client to be observed) is standing erect and facing the observer(the medical examiner), the feet are together, and the arms are hanging at the sides with the palms facing forward

Relative Directional terms

Standard terms of reference are used when anatomists Or medical examiners, describe the location of a certain body part.

Relative means the location of one’s body part is always described in relation to another body part of the same human body.

Terms used	Description
Superior (cranial)	Means towards the head. The leg is superior to the foot.
Inferior (caudal)	Toward the feet. The foot is inferior to the leg.
Anterior (ventral)	Toward the front part of the body. The nose is anterior to the ears.
Posterior (dorsal)	Towards the back of the body. The ears are posterior to the nose.
Medial	Towards the midline of the body. The nose is medial to the eyes
Lateral	Away from the midline of the body. The eyes are lateral to the nose.
Proximal	Toward (nearer) the trunk of the body or the attached end of a limb. The shoulder is proximal to the wrist.
Distal	Away (further) from the trunk of the body or the attached end of a limb. The wrist is distal to the forearm.
Superficial	Nearer to the surface of the body. The ribs are superficial to the heart.
Deep	Further from the surface of the body. The heart is deeper to the ribs.
Peripheral	Away from the central axis of the body. Peripheral nerves radiate away from the brain and spinal cord.

Body parts Regions

The body parts regions are:

Axial : – This is the part of the body that is near the axis of the body. This includes head, neck, thorax (chest), abdomen,
and pelvis.
Appendicular body part: – This is the part of the body out of the axis line. This includes the upper and lower extremities.

The abdomen is divided into nine regions or more, easily divided into four quadrants.

Body planes and sections

Body planes are imaginary surfaces like, plane lines that divide the body into sections. This helps for further identification of specific areas.

Sagittal plane:
– divides the body into right and left half.
– Mid sagittal plane: – divides the body into two equal left and right halves.
– Para sagittal plane: – divides body into two unequal left and right
Frontal plane: – divides the body into asymmetrical antererior
and posterior sections.
Transverse plane: – divides the body into upper and lower body section.
Oblique plane: – divides the body obliquely into upper and lower section.

Cell structure and its functions

Cell: Cell is the basic living structural and functional unit of the
body, and the study of cells is called Cytology.

Cell membrane: This separates the cells from their external environment. Cell membrane also protects the cell from injury.
Cytoplasm: This is the substance that surrounds the organelles and is located between the nucleus and the plasma membrane. This contains raw materials and provides these raw materials to cell organelles for their normal functioning.
Nucleus: This is the storage of genetic information in chromosomes that can be passed onto daughter cells. The nucleus controls all overall cell metabolism and also other activities.
Chromosomes: These also contains genes. Hereditary information is found in the genes. Chromosomes also control cell division and cell growth.
Mitochondria: These is the powerhouse of the entire cell because food is broken down inside them and energy is produced from inside them which helps in performing various processes that need energy.
Vacuoles: These play an important role in the cell enlargement. Vacuoles store food, wastes and also water.

Organelles: Organelles are permanent structures with characteristic morphology that are highly specialized in specific cellular activity.

Tissue structure and function

TISSUE
Cells are highly organized units. But in multi-cultural organisms, they don’t function alone. They work together in groups of similar cells called tissues. A tissue is a group of similar cell and their inter-cellular substance that have the similar embryological origin and they function together to perform a specialized activity. The study of tissues or a science that deals with the study of tissues is called Histology

Tissues are classified according to their structure and their function.

Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue

Epithelial Tissue

Epithelial tissues cover body surfaces, lines the body cavities and ducts and form glands. They are subdivided into:
– Covering & lining epithelium
– Glandular epithelium

Covering and lining epithelium

This forms the outer covering of the external body surface and outer covering of some internal
organs. It lines body cavity, interior of respiratory and gastrointestinal tracts, blood vessels and ducts and make up along with the nervous tissue (the parts of sense organs for smell, hearing, vision and touch). This is a tissue from which gametes
(egg and sperm) develop from.

Covering and lining epithelium are classified based on the arrangement of layers and cell shape.
According to the arrangement of layers covering and lining epithelium is grouped into:
a) Simple epithelium: This is specialized for absorption, and filtration with minimal wear and tear. It is a single layered
b) Stratified epithelium: This is many layered and found in an area with high degree of wear and tear.
c) Pseudo-stratified: This is a single layered but seam to have many layer.

Based on the cell shape covering and lining the epithelium, is grouped into:
a) Squamous Epithelium: – These are flattened and scale like
b) Cuboidal Epithelium:- These are cube shaped
c) Columnar Epithelium: – These are tall and cylindrical
d) Transitional Epithelium: – These are combinations of cell shape found where there is a great degree of distention or expansion, these may be cuboidal to columnar, cuboidal to polyhedral and cuboidal to Squamous

Therefore considering the number of layers and cell shape we can classify covering and lining epithelium in to the following
groups:
Simple epithelium
a) Simple – Squamous epithelium, contain single layer of flat, scale like resemble tiled floor. It is highly adapted to diffusion, osmosis & filtration. Thus, it lines the air sacs of lung, in kidneys, blood vessels and lymph vessels.
b) Simple – cuboidal epithelium, Flat polygon that covers the surface of ovary, lines the anterior surface of lens of the eye, retina & tubules of kidney
c) Simple – columnar epithelium, Similar to simple cuboidal.
It is modified in several ways depending on location & function. It lines the gastro-intestinal tract gall bladder, excretory ducts of many glands. It functions in secretions, absorption, protection & lubrication.

Stratified epithelium
It is more durable, protects underlying tissues form external environment and from wear & tear.
a) Stratified Squamous epithelium: In this type of epithelium, the outer cells are flat. Stratified squamous epithelium is
subdivided in to two based on presence of keratin. These are
Non-Keratinized and Keratinized stratified squamous epithelium. Non-Keratinized stratified squamous epithelium is found in wet surface that are subjected to considerable wear and tear. Example: – Mouth, tongue and vagina. In
Keratinized stratified squamous epithelium the surface cell of this type forms a tough layer of material containing keratin.
Example: skin. Keratin, is a waterproof protein, resists friction and bacterial invasion.
b) Stratified cuboidal epithelium, rare type of epithelium. It is found in seat glands duct, conjunctiva of eye, and cavernous
urethra of the male urogenital system, pharynx & epiglottis. Its main function is secretion.
c) Stratified columnar epithelium, uncommon to the body.
Stratified columnar epithelium is found in milk duct of mammary gland & anus layers. It functions in protection and secretion.

Transitional epithelium
The distinction is that cells of the outer layer in transitional epithelium tend to be large and rounded rather than flat. The feature allows the tissue to be stretched with out breakage. It is found in Urinary bladder, part of Ureters & urethra.

Pseudo stratified epithelium
Lines the larger excretory ducts of many glands, epididymis, parts of male urethra and auditory tubes. Its main function is protection & secretion

Glandular Epithelium

Their main function is secretion. A gland may consist of one cell or a group of highly specialized epithelial cell. Glands can be classified into exocrine and endocrine according to where they release their secretion.
> Exocrine: Those glands that empties their secretion in to ducts/tubes that empty at the surface of covering. Their main products are mucous, oil, wax, perspiration and digestive enzyme. Sweat & salivary glands are exocrine glands.
> Endocrine: They ultimately secret their products into the blood system. The secretions of endocrine glands are always hormones. Hormones are chemicals that regulate various physiological activities. Pituitary, thyroid & adrenal glands are
endocrine.

Classification of exocrine glands

They are classified by their structure and shape of the secretary portion. According to structural classification they are grouped into:

Unicellular gland: Single celled. The best examples are goblet cell in Respiratory, Gastrointestinal & Genitourinary system.
Multicultural gland: Found in several different forms. By looking in to the secretary portion, exocrine glands are grouped into
(a) Tubular gland: If the secretary portion of a gland is tubular.
(b) Acinar gland: If the secretary portion is flask like.
(c) Tubulo-acinar: if it contains both tubular & flask shaped
secretary portion.

Connective tissue

Connective tissues of the body are classified into embryonic connective tissue and adult connective tissue.

Embryonic connective tissue
Embryonic connective tissue contains mesenchyme & mucous connective tissue. Mesenchyme is the tissue from which all other connective tissue eventually arises. It is located beneath the skin and along the developing bone of the embryo. Mucous (Wharton’s Jelly) connective tissue is found primarily in the fetus and located in the umbilical cord of the fetus where it supports the cord.
Adult connective tissue
It is differentiated from mesenchyme and does not change after birth. Adult connective tissue composes connective tissue proper, cartilage, osseous (bone) & vascular (blood)
tissue

a) Connective tissue proper, connective tissue proper has a
more or less fluid intercellular martial and fibroblast. The various forms of connective tissue proper are:
• Loose (areolar) connectives tissue, which are widely distributed and consists collagenic, elastic & reticular fibers and several cells embedded in semi fluid intercellular substances. It supports tissues, organ blood vessels & nerves. It also forms subcutaneous layer/superficial fascia/hypodermis.
• Adipose tissue: It is the subcutaneous layer below the skin, specialized for fat storage. Found where there is loose connective tissue. It is common around the kidney, at the base and on the surface of the heart, in the marrow of long bone, as a padding around joints and behind the eye ball. It is poor conductor of heat, so it decrease heat loss from the body
• Dense (Collagenous) connective tissue: Fibers are closely packed than in loose connective tissue. Exists in areas where tensions are exerted in various directions. In areas where fibers are interwoven with out regular orientation the forces exerted are in many directions. This occurs in most fascia like deeper region of dermis, periosteum of bone and membrane capsules. In other areas dense connective tissue adapted tension in one direction and fibers have parallel arrangement. Examples are tendons and ligaments. Dense connective tissues provide support
& protection and connect muscle to bone.
• Elastic connective tissue: Posses freely branching elastic fibers. They stretch and snap back in to original shape.
They are components of wall of arteries, trachea, bronchial tubes & lungs. It also forms vocal cord. Elastic connective tissue allows stretching, and provides support
& suspension.
• Reticular connective tissue: Lattice of fine, interwoven threads that branch freely, forming connecting and supporting framework. It helps to form a delicate supporting stoma for many organs including liver, spleen and lymph nodes. It also helps to bind together the fibers (cells) of smooth muscle tissue.

b) Cartilage
Unlike other connective tissue, cartilages have no blood vessels and nerves. It consists of a dense network of collagenous fibers and elastic fibers firmly embedded in chondroitin sulfate. The strength is because of collagenous fibers. The cells of a matured cartilage are called chondrocyte.
The surface of a cartilage is surrounded by irregularly arranged dense connective tissue called perichondrium.
Cartilages are classified in to hyaline, fibro and elastic cartilage.
Hyaline cartilage is called gristle, most abundant, blue white in color & able to bear weight. Found at joints over long bones as articular cartilage and forms costal cartilage (at ventral end of ribs). It also forms nose, larynx, trachea, bronchi and bronchial tubes. It forms embryonic skeleton, reinforce respiration, aids in free movement of joints and assists rib cage to move during breathing.
Fibro cartilage: they are found at the symphysis pubis, in the inter-vertebral discs and knee. It provides support and protection.
Elastic cartilage: in elastic cartilage the chondrocyte are located in thread like network of elastic fibers. Elastic cartilage provides strength and elasticity and maintains the shape of certain organs like epiglottis, larynx, external part of the ear
and Eustachian tube.

c) Osseous tissue (Bone)
The matured bone cell osteocytes, embedded in the intercellular substance consisting mineral salts (calcium phosphate and calcium carbonate) with collagenous fibers.
The osseous tissue together with cartilage and joints it comprises the skeletal system.

d) Vascular tissue (Blood tissue)
It is a liquid connective tissue. It contains intercellular substance plasma. Plasma is a straw colored liquid, consists water and dissolved material. The formed elements of the blood are erythrocytes, leukocytes and thrombocytes. The fibrous characteristics of a blood revealed when clotted

Muscle tissue

Muscle tissue consists of highly specialized cells, which provides motion, maintenance of posture and heat production.
Classification of muscles is made by structure and function.
Muscle tissues are grouped in to skeletal, cardiac and smooth
muscle tissue.
– Skeletal muscle tissue are attached to bones, it is voluntary, cylindrical, multinucleated & striated
– Cardiac muscle tissue: It forms the wall of the heart; it is involuntary, un-nucleated and striated.
– Smooth muscle tissue: located in the wall of hallow internal structure like Blood vessels, stomach, intestine, and urinary bladder. It is involuntary and non-striated.

Nervous tissue

Nervous tissue contains two principal cell types. These are the neurons and the neuroglia. Neurons are nerve cells, sensitive to various stimuli. It converts stimuli to nerve impulse. Neurons are the structural and functional unit of the nervous system. It contains 3 basic portions. These are cell body, axons and dendrites. Neuroglia’s are cells that protect, nourish and support neurons. Clinically they are important because they are potential to replicate and produce cancerous growths.

Membranes

Membranes are thin pliable layers of epithelial and/or connective tissue. They line body cavities, cover surfaces, connect, or separate regions, structures and organs of the body. The three kinds of membranes are mucous, serous and synovial.
• Mucous membranes (mucosa) lines body cavity that opens directly to the exterior. It is an epithelial layer.
Mucous membranes line the entire gastro intestine, respiratory excretory and reproductive tracts and constitute a lining layer of epithelium. The connective
tissue layer of mucous membrane is lamina propria. To prevent dry out and to trap particles mucous membranes secret mucous.
• Serous membrane / serosa: contains loose connective tissue covered by a layer of mesothelium. It lines body cavity that does not open directly to the exterior. Covers the organs that lie with in the cavity. Serosa is composed of parietal layer (pertaining to be outer) and visceral layer
(pertaining to be near to the organ). Pleura and pericardium are serous membrane that line thoracic and heart cavity respectively. The epithelial layer of a serious membrane secret a lubricating fluid called serious fluid.
The fluid allows organs to glide one another easily.
• Synovial membrane: Unlike to other membranes this membrane does not contain epithelium. Therefore, it is not epithelial membrane. It lines the cavities of the freely movable joints. Like serious membrane it lines structures that do not open to the exterior. Synovial membranes secret synovial fluid that lubricate articular cartilage at the ends of bones as they move at joints.

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