Describe the different types of epithelial tissue and connective tissue. class 9
Answers
Epithelial Tissue : Different epithelia show differing structures that correlate with their unique functions. For example, in cells lining blood vessels or lung alveoli, where transportation of substances occurs through a selectively permeable surface, there is a simple flat kind of epithelium. This is called the simple squamous epithelium. Simple squamous epithelial cells are extremely thin and flat and form a delicate lining. The oesophagus and the lining of the mouth are also covered with squamous epithelium. The skin, which protects the body, is also made of squamous epithelium. Skin epithelial cells are arranged in many layers to prevent wear and tear. Since they are arranged in a pattern of layers, the epithelium is called stratified squamous epithelium.
Where absorption and secretion occur, as in the inner lining of the intestine, tall epithelial cells are present. This columnar (meaning �pillar-like�) epithelium facilitates movement across the epithelial barrier. In the respiratory tract, the columnar epithelial tissue also has cilia, which are hair-like projections on the outer surfaces of epithelial cells. These cilia can move, and their movement pushes the mucus forward to clear it. This type of epithelium is thus ciliated columnar epithelium.
Cuboidal epithelium (with cube-shaped cells) forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support. Epithelial cells often acquire additional specialisation as gland cells, which can secrete substances at the epithelial surface. Sometimes a portion of the epithelial tissue folds inward, and a multicellular gland is formed. This is glandular epithelium.
Connecting Tissue : Blood is a type of connective tissue. Now, let us look at this type of tissue in some more detail. The cells of connective tissue are loosely spaced and embedded in an intercellular matrix. The matrix may be jelly like, fluid, dense or rigid. The nature of matrix differs in concordance with the function of the particular connective tissue.
Take a drop of blood on a slide and observe different cells present in it under a microscope Blood has a fluid (liquid) matrix called plasma, in which red blood cells (RBCs), white blood cells (WBCs) and platelets are suspended. The plasma contains proteins, salts and hormones. Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body.
Bone is another example of a connective tissue. It forms the framework that supports the body. It also anchors the muscles and supports the main organs of the body. It is a strong and nonflexible tissue. Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
Two bones can be connected to each other by another type of connective tissue called the ligament. This tissue is very elastic. It has considerable strength. Ligaments contain very little matrix. Tendons connect muscles to bones and are another type of connective tissue. Tendons are fibrous tissue with great strength but limited flexibility.
Another type of connective tissue, cartilage, has widely spaced cells. The solid matrix is composed of proteins and sugars.Cartilage smoothens bone surfaces at joints and is also present in the nose, ear, trachea and larynx. We can fold the cartilage of the ears, but we cannot bend the bones in our arms. Think of how the two tissues are different !
Areolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in the bone marrow. It fills the space inside the organs, supports internal organs and helps in repair of tissues.
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Answer:
Epithelial Tissue - Squamous epithelium, Stratified squamous epithelium, cuboidal epithelium, columnar(ciliated) epithelium.
Connective tissue -
Explanation:
EPITHELIAL TISSUES:
Simple Epithelial Tissue
This type of epithelium is composed of a single layer of cells which mainly make up the linings of ducts, tubes and other cavities in the body. Based on the structure of the cell, the simple epithelial tissue is classified into three types viz.:
Squamous epithelium:
It is a simple single-layered epithelium.
Structurally, the squamous epithelium is made up of flat cells with irregular boundaries.
It forms linings of blood vessels and alveoli.
Stratified squamous epithelium:
skin epithelial cells are arranged in many layers to prevent wear and tear since they are arranged in a pattern of layers epithelium is called stratified squamous epithelium.
Cuboidal epithelium:
The tissue is made of cube-shaped cells.
It forms the lining of kidney tubules and ducts of salivary glands.
Columnar epithelium:
It is composed of tall and slender, column-shaped
It forms the lining of the stomach and intestine.
CONNECTIVE TISSUES:
Adipose Tissue:
It is present in skin and organs.
It is composed of fat globules and is characterized by fat storage
It provides insulation due to the fat present.
Areolar tissue and adipose tissue are two types of loose connective tissues where the cells and fibres are loosely scattered in the semi-fluid matrix.
Bone:
Bone is a hard connective tissue which forms the framework of the body.
It has a rigid matrix rich in calcium and collagen fibres.
Functions include protection, support, facilitates movements and serves as a site for blood cell production.
Cartilage:
Cartilage is made of chondrocytes with dense, flexible intercellular materials.
In the majority of vertebrates, cartilages in embryos get replaced by bones on maturity.
They are present at the tips of external ears, bronchi, vertebral column, etc.
Blood:
Blood is the only fluid connective tissue composed of blood cells (RBC, WBC, and platelets) and plasma.
Functions: Transportation, defence, blood clotting and helps in homeostasis.
Blood, bone, and cartilage are specialized connective tissues.