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Mast cells are also known as a mastocytes. It is a type of white blood cell (WBC). Mast cells release histamine and other substances during inflammatory (redness and swelling) and allergic reactions.

Permanent tissues possess the following characteristics: 

(i) Cells of this tissue can be living or dead. 

(ii) Cell walls may be thin or thick. 

(iii) Intercellular spaces may be present or absent. 

(iv) Metabolic activities are relatively slow. 

(v) Vacuoles in the cells are prominent. 

Examples of permanent tissues are parenchyma, collenchyma and sclerenchyma (simple tissues) and xylem and phloem (complex tissues).

Simple permanent tissue such as parenchyma, collenchyma and sclerenchyma are a few layers of cells located beneath the epidermis.

Smooth muscle tissues are located in the iris of the eye, in ureters and in the bronchi of the lungs. 

The smooth muscle tissue forms organs which shape to perform various bodily functions.

(i) Multinucleate muscle fiber: 

Skeletal or striated muscles have many nuclei. 

Skeletal muscles are attached to bones by tendons, and they produce all the movements of body parts in relation to each other. 

(ii) Spindle-shaped muscle fiber: 

Smooth or unstriated muscles are spindle shaped with single nucleus. Spindle cell sarcoma is a type of connective tissue cancer in which the cells are spindle-shaped when examined under a microscope.

Sieve tubes of phloem are formed by end to end fusion of cells with perforated transverse wall.

The sclerenchyma tissue is made of dead cells. The cells are without cytoplasm and nucleus that are devoid of cytoplasm and nucleus. Space between cells (intercellular space) absent due to deposition of lignin.

Functions of xylem: 

(i) To carry water and mineral salts upwards from the root to different parts of shoots. 

(ii) To provide mechanical support to the plant as the walls of tracheids, vessels, and fibres of xylem are lignified.

Types of elements found in xylem are: 

tracheids, vessels, xylem parenchyma, and xylem fibre.

Epidermis 

• Epidermis forms one cell thick outermost layer of various body organs of plants such as leaves, flowers, stems and roots. 

• Epidermis is covered outside by cuticle. Cuticle is a water- proof layer of waxy substance called as cutin which is secreted by the epidermal cells. 

• Cuticle is very thick in xerophytes. 

• Cells of epidermis of leaves are not continuous at some places due to the presence of small pores called as stomata. 

• Each stomata is guarded by a pair of bean-shaped cells called as guard cells. These are the only epidermal cells which possess chloroplasts, the rest being colourless.

Functions of Epidermis 

• The main function of epidermis is to protect the plant from desiccation and infection. 

• Cuticle of epidermis cuts the rate of transpiration and evaporation of water and prevents wilting. 

• Stomata in epidermis allow gaseous exchange to occur during photosynthesis respiration. 

• Stomata also helps in transpiration. 

Cork or Phellem 

• In older roots and stems, tissues at the periphery become cork cells or phellem cells. 

• Cork is made up to dead cells with thick walls and do not have any intercellular spaces. 

• The cell walls in cork deposit waxy substance called as suberin. 

• The cells of cork become impermeable to water and gases due to the deposition of suberin. 

• The cork cells are without any protoplasm but are filled with resins or tannins.

Functions of Cork : 

• Cork is protective in function. Cork cells prevent desiccation, infection and mechanical injury. 

• Imperviousness, lightness, toughness, compressibility and elasticity make the cork commercially valuable. 

• Cork is used for insulation, as shock absorber in linoleum. 

• Cork is used in the making of a variety of sport goods such as cricket balls, table tennis, shuttle cocks, wooden paddles etc.

Connective tissues are fibrous in nature. They include blood, bone, ligament, cartilage, areolar and adipose tissues. These help in binding other tissues together. They also provide support to other tissues.

Blood has plasma and blood cells. The blood cells suspended in the plasma include RBC’s, WBC’s and platelets. Blood flows within blood vessels, and transports gases, digested food, hormones and waste materials to different parts of the body.

Bone cells are embedded in a hard matrix composed of calcium and phosphorus compounds. Bones anchor the muscles and support the main organs of the body.

Two bones can be connected to each other by another type of connective tissue called ligament. Ligaments are tough and elastic. They provide strength and flexibility. Tendons connect muscles to bones and are another type of connective tissue. Tendons are tough and non-elastic, and provide great strength and limited flexibility.

Cartilage has widely spaced cells suspended in a matrix of proteins and sugars. It is found in the nose, ears, and the rings of the trachea to give flexibility.

Areolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in the bone marrow. It helps in repair of tissues.

Adipose tissue contains cells filled with fat globules. It is found below the skin and acts as an insulator.

Muscle tissues consists of elongated cells also called muscle fibres. This tissue is responsible for movement. Muscles contain special proteins called contractile proteins which contract and relax to cause movement. These are elastic in nature they have tensile strength. These muscles can be voluntary or involuntary in function. Muscular tissues are of three kinds namely striated muscles, unstriated muscles and cardiac muscles.

Striated muscle cells are long, cylindrical, unbranched and multinucleate. These are voluntary muscles.

Smooth muscles or involuntary muscles are found in the iris of the eye, in ureters and in the bronchi of the lungs. These are also called unstriated muscles. The cells are long with pointed ends and uninucleate.

Hear muscles or cardiac muscles are cylindrical, branched and uninucleate.