"AKC SCIENCE CLASSES"
CLASS 09 TH (CBSE AND MP BOARD)
CHAPTER 06
TISSUES
BASIC CONCEPTS
1) A group of similar cells that perform or help to perform a common function and have a common origin is called a tissue.
2) Plant tissues are of two main types-- Meristematic tissues and Permanent tissues.
3) A group of cells that are preparing to divide, or are in the process of multiplication or have the capacity to divide is known as meristematic tissue.
4) Meristematic tissues can be classified on the basis of their position into apical (shoot and root apex), lateral (cambium, cork cambium) and intercalary meristems.
5) Permanent tissues can be of three types-- simple tissues, complex tissues, and special tissues.
6) Simple tissues are made up of one type of cells and they perform the same function whereas complex tissues are made up of more than type of cell and they work together to perform a particular function.
7) Parenchyma cells are thin walled cells with intercellular spaces. They store food.
8) Collenchyma consists of living cells which are thickened at the corners with pectin and cellulose. It gives mechanical strength and flexibility to the plant organ.
9) Sclerenchyma consists of dead cells which have deposition of lignin. It provides mechanical strength.
10) Xylem conducts water and minerals. It is also known as wood. It consists of sieve tubes, companion cells, phloem fibers and phloem parenchyma.
11) Phloem conducts foods materials. It is also known as bast. It consists of sieve tubes, companion cells, phloem fibers and phloem parenchyma.
12) Animal tissues are of four different types depending upon their structure and functions. They are epithelial, connective, muscular and nervous tissues.
13) Epithelial tissue covers the entire body externally as well as internally.
14) In simple epithelium, cells are arranged in a single layer whereas in stratified epithelium cells are arranged in more than one layer.
15) Squamous epithelium, cells are arranged in a single layer whereas in stratified epithelium cells are arranged in more than one layer.
16) On the basis of their function epithelial tissues may be sensory (eye, ear), germinal (testis, ovary) , ciliated (respiratory tract), glandular (sweat gland).
17) Connective tissue is filled with a non-living matrix. It is the most abundant body tissue.
18) Areolar tissue is commonly known as packaging tissue ; Adipose tissue stores fat ; Tendon connects muscle to a bone whereas ligament connects bone to bone.
19) Cartilage is semi-rigid and flexible whereas bone is solid, rigid with deposition of inorganic salt (like calcium and phosphorus).
20) Fluid connective tissue has fibreless matrix. Blood consists of plasma and blood cells.
21) RCB transports O2 and CO2 ; WBC provides immunity to the body whereas blood blood platelets help in blood coagulation.
22) Lymph is like plasma, but it lack RBC and blood platelets. It contains large number of lymphocytes.
23) Muscles are capable of contraction and relaxation in response to chemical stimuli. They may be
- Striated-cylindrical, unbranched, multinucleate, attached to skeleton ;
- smooth-spindle shaped, uninucleate;
- cardiac-striated, cylindrical, uninucleated with intercalated discs.
25) The region of union of the axon endings of one neuron with the dendrite of another neurons is called synapse.
