Tissue of the body : Tissue of the body There are four types of tissues in the body: : There are four types of tissues in the body: Epithelial tissue.
Nervous tissue. General characteristics of epithelium : General characteristics of epithelium It lines cavities and covers surface
It consists entirely of cells, with little intercellular substance.
The cells lie on a basement membrane
No blood vessel enter inbetween cells.
its superficial layers (degeneration), but the dead regenerated (replaced by new cells) from the basal layers.
Its origin ectodermal, mesodermal, or endodermal. Simple squamous epithelium : Simple squamous epithelium formed of one layer of flat cells with flattened nuclei and with irregular borders
it forms a thin smooth surface for the easy passage fluid or gasses (blood or filtration of urine in kidney). Simple cubical (cuboidal) : Simple cubical (cuboidal) laying on a basement membrane.
The cells have large, central, rounded nuclei lying at the same distance from the basement membrane Simple columnar epithelium : Simple columnar epithelium one layer of cells like columns lying on a basement membrane. nuclei are oval, basal. Mainly concerned with secretion, absorption, protection. Pseudo stratified columnar : Pseudo stratified columnar one layer of columnar cells.
the cells becomone layer of columnar cells.
the cells become overcrowded on each other.
nuclei usually occupy the widest part of the cell
e overcrowded on each other.
nuclei usually occupy the widest part of the cell Stratified epithelium : Stratified epithelium formed of two or more layers (strata) of cells. It is a protective type of epithelium
Stratified squamous epithelium
Stratified columnar epithelium Stratified squamous epithelium : Stratified squamous epithelium formed of several layers up to 30 or more. Non-keratinized basal cells are cubical or columnar, the intermediate cells are polygonal and gradually flatten towards the top where become squamous
Keratinized type flat cells of the top layer gradually change to horny layer, as in the epidermis of skin. Transitional epithelium : Transitional epithelium stratified type of epithelium
superficial cells are cubical. The intermediate layers consist of polyhedral cells. The basal cells are columnar with no apparent basement membrane. Stratified columnar epithelium : Stratified columnar epithelium cells of superficial layer are columnar, intermediate cells are polyhedral and basal cells are columnar or cubidal. Connective tissue : Connective tissue Connective tissues serve a variety of functions including: : Connective tissues serve a variety of functions including: 1) Supportive: as a structural framework for cells, tissues and organs.
2) Nutritive: as a matrix (substrate) for blood vessels and
3) Lubricative: as an agent for the relatively friction-free
movement of tissues and organs. (Consider the ease with
which you are able to move muscles and bones, and without
painfully distorting the overlying skin.)
4) Reparative : as an important element in wound healing
and scar formation. The three types of connective tissue : The three types of connective tissue CONNECTIVE TISSUE PROPER
BONE Slide 17: The components of connective tissue are:
3- matrix (ground substance) types : types 1- Loose (areolar) C.T.
-called loose because it is flexible
Widely distributed all over the body Slide 19: 2- Adipose (fatty) C.T.
- White and brown
Groups of fat cells
Separated by septa (carry blood vessels, nerves,
Presents in abdomen Slide 20: 3- Mucoid (mucous) C.T.
Network of young fibroblasts
Embedded in intercellular space (mucin)
Present in umbilical cord Slide 21: 4- Dense (white fibres) C.T.
Resist to stretch
White due to high content of collagen
Matrix is minimal
Present in tendons and cornea Slide 22: 5- yellow (elastic fibres) C.T.
Yellow in color
Matrix is low
Present in large arteries, vocal cord. Slide 23: 6- Reticular C.T.
Reticular cells and reticular fibres
Matrix very very low
Present in liver, spleen, bone marrow. Glandular epithelium : Glandular epithelium classified according to presence or absence of ducts
classified according to number of cells
classified according to shape of secretion part
classified according to nature of secretion
classified according to mode of secretion Composed of cells that are specialized to produce and
secrete substances Slide 26: Mechanism of Glandular Secretions Merocrine glands
sweat glands Apocrine glands
portions of cells
mammary glands Holocrine glands
sebaceous glands (the way in which the secretory products leave the cell) Neuro-epithelium : Neuro-epithelium special type of epithelium which during development, has become highly specialized for perception of external stimuli (sensory receptors). Slide 29: Neuron Slide 30: found in:
(brain, spinal cord, and peripheral nerves)
Nervous tissue consists of two kinds of cells:
neurons and neuroglial
Neuron The basic function is transmit information. There are approximately 28 billion neurons in the human body
Basic cells are Neuron:
consists of cell body and cell processes –
dendrite (receive) and axon (send).
neuroglia cells are supporting cells
nerve impulses. It contains receptor specialized for
receiving different types of stimuli. Slide 32: Function:
To rapidly regulate and integrate the activities of the different parts of the body • Sensory tissues
• Regulatory tissues
– Coordinate body functions
– Keep track of body conditions
• Transmit electrical signals Types of nerve cells : Types of nerve cells The neurons may be classified according to the number of their cell processes into:
These are flask-shaped, having a single process which divides into a central (axon) and a peripheral branch (dendrite).
Unipolar neurones are very common in the peripheral nervous system Slide 34: 2- Bipolar:
Have two processes extended from the cell body. e.g. ratinal cell, and olfactory epithelium.
All neurones in the nervous system of a human embryo are bipolar Slide 35: 3- Multipolar:
Have several processes.
Multipolar neurones are the most common type of neurone in the brain and spinal cord of mammals Slide 37: Important differences between axons and dendrites: Axons
Take information away from the cell body
Generally only 1 axon per cell
Can have myelin
Branch further from the cell body Dendrites
Bring information to the cell body
Usually many dendrites per cell
No myelin insulation
Branch near the cell body Function of epithelial tissues : Function of epithelial tissues Protection against injuries, bacteria, chemicals and water as epithelium of skin and stomach.
Secretion as glandular epithelium of pancreas, prostate, salivary and endocrine glands.
Absorption as the cells in intestine and kidney.
Sensation as the taste buds.
Reproduction as the cells of the testis and ovary.
Excretion as the cells of kidney and sweat glands.
Covering surface or lining cavities.