Differentiation of cells & Diversity of animal tissues

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 .

Epithelial 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 :

  1. Absorbing the water and digested food , as in the lining of digestive canal .
  2. Protecting the cells ( which they cover ) from drought and pathogens ( as microbes , as in the skin epidermis .
  3. 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 .

Animal tissues

Animal tissues

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 .

Connective tissues

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 .

Muscular tissues

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 .

Smooth 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 .

Skeletal muscles  

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 .

Cardiac muscles

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 .

Nervous tissues

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

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

Cell fractionation is one of the modern technologies used to :

  1. Study each type of different cells forming a certain tissue .
  2. Study the different organelles forming one type of cells and this includes the site of these organelles , their functions and their components .
  3. Study the biological macromolecules like enzymes .
  4. 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 .

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