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CHAPTER III
PDL 101 HUMAN ANATOMY & PHYSIOLOGY
Ms. K. GOWRI. M.Pharm.,
Lecturer. Tissues:
Tissues of the body consists of large number of cells.
They are classified according to size,shape and functions of these cell.
4 main types of tissues are there. They are
1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nervous tissue Epithelial tissue:
This tissue is found covering the body and lining
cavities and tubes.
Also found in glands.
Functions:
1.Protection
2.Secretion
3.Absorption
Epithelial tissue may be:
simple‐a single layer of cells.
Stratified‐a several layer of cells.
Simple epithelium:
Consists of single layer of cells and divided into 4 types .
Squamous epithelium: composed of single layer of flattened cells.
Diffusion takes place freely through this thin , smooth, inactive lining of the foll structures.
1. Heart
2. Blood vessels
3. Lymph vessels
4. Alveoli of the lungs.
Cuboidal epithelium: consists of cube‐shaped cells fitting together lying on a basement membrane.
It is involved in secretion , absorption and excretion.
Columnar epithelium: This is formed by single layer of cells , rectangular in shape.
Some absorb the products of digestion and other secrete mucus.
mucus is a thick substance secreted by columnar cells called goblet cells.
Ciliated epithelium: found by columnar cells which has fine , hair like processes called cilia.
The wave like movement of many cilia propels the contents of the tubes , which lie in one direction only.
This is found lining the uterine tubes and most of the respiratory passages. In uterine tubes the cilia propel ova towards the uterus and in respiratory passages propel mucus towards the throat.
Stratified epithelia:
Main function of this to protect underlying structures from mechanical wear and tear.
There are 2 main types:
Stratified squamous epithelium:
Composed of number of layers of cells of different shapes.
In the deepest layer the cells are mainly columnar and they grow towards the surface, they become flattened and then shed.
1. Non‐keratinized stratified epithelium. 2. Keratinized stratified epithelium.
Transitional epithelium: composed of several layers of pear‐shaped cells and found lining the urinary bladder.
Connective tissue:
It is the most abundant tissue in the body.
Cells forming the tissues are more widely separated from each other than these forming epithelium.
There may or may not be fibres present in the matrix, which may be of a semisolid jelly like consistency or dense and rigid depending upon the position and function of tissue.
Functions of connection tissue:
Binding and structural support.
Protection.
Transport.
Insulation.
Cells of connective tissue:
• Fibroblasts
• Fat cells
• Macrophages
• Leukocytes
• Mast cells
Fibroblasts: are large flat cells with irregular processes.
They produce collagen and elastic fibres and a matrix of extracellular material.
Very fine collagen fibres sometimes called reticulin
fibres are found in very active tissue , such as the liver and lymphoid tissue.
Collagen fibres formed during healing shrink as they grow old , sometimes interfering with the function of organ involved and with adjacent structures.
Fat cells: also known as adipocytes and are especially abundant in adipose tissue.
Macrophages: they are irregular‐shaped cells with granules in the cytoplasm.
Some are fixed i.e attached to connective tissue fibres
and others are motile.
They are actively phagocytic , engulfing and digesting cell debris , bacteria and other foreign bodies.
Eg: Monocytes in blood , phagocytes in the alveoli of the lungs , kupffer cells in liver sinusoids , fibroblasts in lymph nodes and spleen and microglial cells in the brain
Leukocytes: White blood cells are normally found in small numbers in healthy connective tissue but migrate in significant numbers uring
infection when they play an important part in tissue defence.
Lymphocytes synthesize and secrete antibodies into the blood in the presence of foreign material such as microbes.
Mast cells: These cells are similar to basophil leukocytes. They are found in connective tissue and under the fibrous capsule of some organs. eg: liver and spleen
They produce granules containing heparin , histamine an other substance, which are released when the cells are damaged by disease or injury.
Histamine is involved in local and general inflammatory reactions. It stimulates the secretion of gastric juice and is associated with the development of allergies and hypersensitivity states.
Heparin prevents coagulation of blood, which may aid the passage of protective substances from blood to affected tissues.
Loose connective tissue: The matrix is described as semisolid with many fibroblasts and some fat cells, mast cells and macrophages separated by elastic and collagen fibres.
It connects and support other tissues for example:
Under the skin
Between the muscles
Supporting blood vessels and nerves
In the alimentary canal
In glands supporting secretory cells
Adipose tissue: It consists of fat cells containing fat globules, in a matrix of areolar tissue.
Two types:
1.White adipose tissue: This makes up 20‐25% of boy weight in well nourished adults. The amount of adipose tissue in an individual is determined by the balance between energy intake and expenditure.
2.Brown adipose tissue: this is present in new born.
It has more extensive capillary network than white adipose tissue.
When brown adipose tissue is metabolised , it produces less energy and considerably more heat than fat.
In adults it is present in small amounts.
Dense connective tissue:
Fibrous tissue.
Elastic tissue.
Cartilage:
3 types:
1.Hyaline cartilage
2.Fibro cartilage
3.Elastic fibrocartilage
Hyaline cartilage is found:
On the surface of the parts of the bones that forms joints .
Forming the costal cartilages, which attach the ribs to the sternum.
Forming part of the larynx, trachea and bronchi.
Fibrocartilage:
It is a tough, slightly flexible tissue found:
As pads between the bodies of the vertebrae called intervertebral discs.
Between the articulating surfaces of the bones of the knee joint, called semilunar cartilages.
On the rim of the bony sockets of the hip and shoulder joints, deepening the cavities with out restricting movement.
As ligaments joining bones.
Elastic cartilage:
The cells lie between the fibres.
It forms the pinna or lobe of the ear, epiglottis and part of the tunica media of blood vessel walls.
Muscle tissue:
3 types of muscle tissue, which consists of specialised contractile cells.
• Skeletal muscle
• Smooth muscle
• Cardiac muscle
Skeletal muscle tissue: This may be described as skeletal, striated, striped or voluntary muscle.
Called as voluntary because contraction is under concious
control.
When skeletal muscle is explained the cells are found to be roughly cylindrical in shape and may be as long as 35cm.
Each cell commonly called a fibre, has several nuclei situated just under the sarcolemma or cell membrane of each muscle fibre.
The muscle fibres lie parallel to one another to one another an they show well‐marked transverse dark and light bands, hence the name striated or striped muscle contains:
Bundles of myofibrils, which consists of filaments of contractile proteins including actin and myosin.
Many mitochondria which generate chemical energy from glucose and oxygen.
Gycogen‐ a carbohydrate store which is broken down into glucose.
Myoglobin‐ a unique oxygen‐bining protein molecule, similar to haemoglobin in red bloo cells which stores oxygen.
A myofibril has a repeating series of dark and light bands consists of units called sacromeres.
Sacromere represents the smallest functional unit of a skeletal muscle fibre and consists of
1.Thin filaments of actin
2.Thick filaments of myosin.
Smooth muscle tissue:
May also describe as non‐striated or involuntary.
Found in the walls of hollow organs
1.Regulating the diameter of blood vessels and parts of the respiratory tract.
2.Propelling contents of the uterus, ducts of glands and alimentary tract.
3.Expelling contents of the urinary bladder.
Functions of muscle tissue:
When the fibres contract they become thicker and shorter.
Skeletal muscle fibres are stimulated by motor nerve impulses originating in the brain or spinal cord and ending at the neuromuscular junction.
Smooth and cardiac muscle have the intrinsic ability to initiate contraction.
When muscle fibres contract they follow the all or none law. i.e each fibre contracts to its full capacity or not at all.
In order to contract when it is stimulated , a muscle fibre must have an adequate blood supply to provide suffiecient
oxygen, calcium and nutritional materials and to remove waste products.
Features of skeletal muscle:
Individual muscles and group of muscles have been given names that reflect certain characteristics:
1.Shape of the muscle‐ the trapezius is shaped like a trapezium.
2.The direction in which the fibres run‐the oblique muscle of the abdominal wall.
3.The position of the muscle.
4.The movement produce by contraction of a muscle.
5.The number of points of attachment of a muscle.
6.The names of the bones to which the muscle is attached.
Nervous tissue:
There are two types of tissue:‐
1.Excitable cells‐called neurons and they initiate, receive, conduct and transmit information.
2.Non‐excitable cells‐support the neurons.
Properties:
Neurons‐these are a vast number of cells.
Neurons have the characteristics of irritability and conductivity.
Irritability: is the ability to initiate nerve impulses in response to stimuli form
1.Outside the body‐eg: touch , light waves 2.Inside the body‐eg: change in concentration of carbondioxide in the blood alters respiration.
In the body this stimulation may be described as partly electrical and partly chemical.
Conductivity: means the ability to transmit an impulse.
Axons and dendrites are the extensions of cell bodies and form white matter of the nervous system.