NCERT Revision Notes for Chapter 6 Tissues Class 9 Science
CBSE NCERT Revision Notes1
Answer
→ The contraction and relaxation of these cells result in movement.
→ Blood flows and carries various substances from one part of the body to the other.
→ Blood and muscles are both examples of tissues found in our body.
→ Different types of animal tissues, such as epithelial tissue, connective tissue, muscular tissue and nervous tissue.
→ Blood is a type of connective tissue, and muscle forms muscular tissue.
2
Answer
→ Always grows on some other types of tissue.
→ Cells of epithelium are set very close to each other and the tissue rests on a non-cellular basement membrane.
→ Consists of single layer of cells.
→ Blood vessels are absent and non-nervous in nature.
→ It covers all the organs and lines the cavities of hollow organs like stomach.
→ It is primarily protective in function.
Types of Epithelium
→ Epithelium tissues are classified as Squamous epithelium, Cubical epithelium, Columnar epithelium and Ciliated epithelium.
(i) Squamous epithelium:
→ It is also called pavement epithelium.
→ Cells arranged end to end like tiles on a floor.
→ Cells are polygonal in surface view.
→ It forms the delicate lining of cavities (mouth, oesophagus, nose, pericardium, alveoli etc.) blood vessels and covering of the tongue and skin.
→ Epithelial cells are arranged in many layers (stratum) to prevent wear and tear in skin. This pattern is stratified squalors epithelium.
(ii) Cubical epithelium
→ They are cube like cells that fit closely, cells look like squares in section, but free surface appears hexagonal.
→ It is found in kidney tubules, thyroid vesicles & in glands (salivary glands, sweat glands).
→ It forms germinal epithelium of gonads (testes & ovaries).
→ It involves in absorption, excretion & secretion. It also provides mechanical support.
(iii) Columnar epithelium
→ Columnar means ‘pillar-like’ epithelium. It forms lining of stomach.
→ Small intestine & colon, forming mucous membranes.
→ Border of micro villi is present at the free surface end of each cell which increases absorption efficiency in small intestine.
(iv) Ciliated epithelium
→ Cells may be cubical or columnar.
→ On its free surface are present protoplasmic outgrowths called cilia.
→ It helps in the movement of ova in the fallopian tube.
3
Answer
→ The cells of the connective tissue are widely spaced and embedded in an intercellular matrix.
→ The mature of matrix decides the function of tissue.
→ White and yellow fibres are present in the matrix.
→ Their basic function is to provide support to different organs & keeping them in place.
4
Answer
• Blood and lymph
→ Blood is a connective tissue, fluid matrix of blood is plasma having wandering or floating cells, called corpuscles, blood helps in the transportation of various materials such as nutritive substances, gases, excretory products, hormones etc.
• Plasma
→ It forms 55% part of blood. It constitute of 90-91% of water, 7% of protein (Albumin, fibrinogen, globulin), 0.9% of inorganic salt etc.
• Corpuscles
→ Forms 45% part of blood.
• RBCs
→ They are also called as erthyrocytes, containing red coloured respiratory pigment called haemoglobin that helps in transportation of oxygen.
• WBCs (Leucocytes)
→ They are also called as ‘Soldiers of the body’.
→ They are irregular, amoeboid, phagocyte cells that protect our body by engulfing bacterial & other foreign particles.
→ They are of five types: Monocytes, Lymphocytes, Basophiles, Neutrophiles, Eosinophils.
Blood platelets or thrombocytes
→ They are spindle shaped cells which are involved in clotting of blood.
5
Answer
→ It is hard connective tissue that forms supportive framework of the body.
→ It is of two types: Bone and Cartillage.
• Bone
→ Matrix of bone is very hard because of salts such as calcium phosphate, CaCO3 (60-70%) etc. and a protein ossein.
→ Bone cells (osteoblasts) are embedded in this hard matrix.
→ Matrix is deposited in the form of concentric layers of lamellae formed round a central canal, the done cells occupy small spaces between the concentric layers of matrix.
→ The long bones are usually hollow containing cavity called as marrow cavity. It is full of bone marrow.
• Cartilage
→ This tissue is elastic, less harder as compared to bones.
→ Elasticity is due to presence of chondrin (protein). Cells are called as chondroblast, which are widely spaced and matrix is reinforced by fibres.
→ It occurs at joint of bones, in the nose, ear, trachea & larynx.
→ It provides flexibility and great tensile strength.
6
Answer
→ It is the most abundant type of connective tissue.
→ It is further divided into two types i.e Yellow fibrous connective tissue and White fibrous connective tissue.
• Yellow fibrous connective tissue
→ They are very elastic due to the presence of a network of yellow fibres in its matrix called as ligament which attaches bone to bone.
• White fibrous connective tissue
→ They are very little matrix containing abundant white fibres forming layers.
→ Bundles of this tissue are called as tendons, which attaches muscles to the bones.
7
Answer
→ It is the most distributed connective tissue in the body.
→ This tissue fills spaces inside organs and is found between the skin & muscles, around blood vessels, nerves and in the bone marrow.
8
Answer
→ These are oval and round cells, filled with fat globules.
→ The cells are called as adipocytes.
→ It is found in subcutaneous layer below the skin, around the heart, brain and below the eyeballs.
→ It acts as an insulator and prevents loss of heat from the body.
9
Answer
→ Movements are brought about in our body with the help of muscular tissues.
→ They are long fibre-like cells called muscle fibres.
→ They are capable of contraction or relaxation.
→ Types of Muscular Tissue are Striated muscles, cardiac muscle fibres and Non-striated muscles.
(i) Striated muscles
→ They are also called as voluntary muscles because these are under the control of one’s will.
→ Muscle fibres or cells are multinucleated and unbranched.
→ Each fibre is enclosed by thin membrane which is called as sarcolemma.
→ Cytoplasm is called as sarcoplasm.
→ These muscles get tired and need rest.
(ii) Cardiac muscle fibres
→ They are only involuntary muscles.
→ Only found in the walls of heart.
→ Their structure is in between the striated and non-striated muscles.
→ They are uninucleated and branched. Branches are united by intercalated disc.
→ In these muscles rhythmic contraction and relaxation occurs throughout the life.
(iii) Non-striated muscles
→ They are involuntary muscles also called as smooth muscles.
→ These muscle fibres are uninucleated and spindle shaped.
→ They are not enclosed by membrane but many fibres are joined together in bundles.
→ Such muscles are found in the walls of stomach, intestine, urinary bladder, bronchi, iris of eye etc.
→ Peristaltic movements in alimentary canal are brought about by smooth muscles.
10
Answer
→ They are highly specialized tissue due to which the animals are able to perceive and respond to the stimuli.
→ Their functional unit is called as nerve cell or neuron.
→ Cell body is called cyton which is covered by plasma membrane.
Dendron
→ Short hair like extensions rising from cyton are Dendron which are further subdivided into dendrites.
Axon
→ Axon is long, tail like cylindrical process with fine branches at the end.
→ Axon is covered by a sheath.
→ Axon of one neuron is very closely placed to the dendrons of another neuron to carry impulses from one to another neuron in the form of electrochemical waves.
→ This close proximity is called as synapse.