Differentiation of cells & Diversity of animal tissues
Animal tissues can be differentiated into basic types , each of them matches with the function it performs , such as Epithelial tissues , Connective tissues , Muscular tissues and nervous tissues .
Location : They cover the outer surface of the body and line the body’s internal cavities .
Structure : They are composed of a great number of closely adjacent cells connected by little interstitial ( intercellular ) substance .
Epithelial tissues functions
They perform different functions depending on their site in the body , such as :
- Absorbing the water and digested food , as in the lining of digestive canal .
- Protecting the cells ( which they cover ) from drought and pathogens ( as microbes , as in the skin epidermis .
- Secreting the mucus that makes the cavities they line smooth and moist , as in the digestive canal and trachea .
Types : They are divided into two main types according to their shape and structure , Simple epithelial tissue and Compound ( or stratified ) epithelial tissue .
Simple epithelial tissue
Its cells are organized in one layer , such as Simple squamous tissue , Simple cuboidal tissue and Simple columnar .
Simple squamous tissue consists of one layer of flattened cells such as the lining ( endothelium ) of the blood capillaries and the wall of alveoli in the lungs .
Simple cuboidal tissue consists of one layer of cuboidal cells such as the lining of the kidney tubules .
Simple columnar consists of one layer of columnar cells such as the lining of the stomach and intestines .
Compound ( or stratified ) epithelial tissue
Its cells are organized in several layers such as the stratified squamous tissue .
The stratified squamous tissue consists of several layers of compact cells above each others and its surface layer is squamous , such as the tissue of skin epidermis .
Structure : They are made up of some what distant cells that immersed in an intercellular substance , they may be fluid , semi-solid or solid .
Types : They are divided according to the kind of the intercellular substance into three types which are Connective tissue proper , Skeletal connective tissue and Vascular connective tissue .
Connective tissue proper
Characteristics : It gathers between being fairly solid and quite elastic .
Function : Connecting the different body tissues and systems with each other , So , it is widely spread such as the dermis of skin and mesentries .
Skeletal connective tissue
Characteristics : Its intercellular substance is solid in which calcium deposits in case of bones .
Functions : Supporting the body such as the bones and cartilages .
Vascular connective tissue
Characteristics : its intercellular substance is fluid .
Function : Transporting the digested food and excretory substances , such as the blood and lymph .
Structure : They are made up of cells known as muscular cells or muscle fibres , which are distinguished from other body cells by their abilities of contraction relaxation , So , this helps the organism to move .
Types : they are divided into three types which are Smooth muscles , Skeletal muscles and Cardiac muscles .
Structure : They consist of unstriated involuntary muscle fibres .
Location : They present in the wall of viscera such as wall of digestive canal , urinary bladder and blood vessels .
Structure : They consist of striated voluntary muscle fibres .
Location : They are usually connected with the skeleton , such as the muscles of arms , legs and trunk .
Structure : They consist of striated involuntary muscle fibres , They contain intercalated discs that bind the muscle fibres together and make the heart beats in a rhythmic way as one functional unit .
Location : They present in the heart wall only .
Structure : They consist of cells called nerve cells ( or neurons ) , The nerve cell is the building and functional unit of the nervous system .
Function : Receiving both the internal and external sensory stimuli and conduct them to the brain and spinal cord , then transmitting the motor impulses to the effector organs ( muscles or glands ) , Therefore , nervous tissues are responsible for different activities of body organs .
Science , Technology and society
Stem cells are the cells that have the ability to form any other type of specialized cells , such as muscle cells , liver cells , nerve cells and skin cells , according to specific environmental treatments at the laboratory , Stem cells are formed during the early stages of the fetus development .
Role of stem cells in treating of intractable diseases :
They are used to produce dopamine substance used to treat some nervous diseases as Parkinson disease .
They are transplanted to give cardiac muscle cells as a compensation about the decrease of secretion of this hormone by pancreas for diabetes patients .
Cell fractionation is one of the modern technologies used to :
- Study each type of different cells forming a certain tissue .
- Study the different organelles forming one type of cells and this includes the site of these organelles , their functions and their components .
- Study the biological macromolecules like enzymes .
- Study the biological processes occur inside the cell .
Ways of using cell fractionation technology :
Cell fractionation technology depends on using ultracentrifuge apparatuses to separate cell organelles at different speeds depending on the different densities of these organelles .