Ch 10Animal Tissue — Class 11 Biology, concept-first.

Histology is the branch of biology that studies the structure and arrangement of tissues. Recall that a tissue is a group of cells that share a common embryonic origin and are similar in structure, an…

Epithelial tissue (epi = above/upon, thelium = layer of cells) forms a continuous covering or lining over the outer surface of the body and over the inner surfaces of organs and cavities.

Simple epithelium consists of just one layer of cells, all resting directly on the basement membrane. Based on the shape of its cells and the specific job it performs, simple epithelium is further div…

Squamous epithelial tissue is made of flat, thin, polygonal cells with an irregular, serrated (saw-toothed) margin.

Cuboidal epithelium is built of cube-shaped cells, each with a single, roughly spherical nucleus placed at its centre.

Columnar epithelium is made of tall, pillar-like cells. Each cell narrows towards its inner (basal) end and broadens out flat at its free (outer) end, and this free surface typically carries a large n…

Ciliated epithelium is made of cuboidal or columnar cells whose broad free end bears numerous hair-like cilia, while the narrower opposite end rests on the basement membrane.

Glandular epithelium is made up of secretory cells that may be columnar, cuboidal or pyramidal in shape.

Sensory epithelial tissue is built from a modified form of columnar cells together with elongated neurosensory cells, and carries fine sensory hairs at its free end.

Germinal epithelium is composed of cells that divide meiotically to produce haploid gametes, rather than dividing to renew a lining as most epithelial tissue does.

Epithelial cells do not simply sit next to one another — they are physically connected to their neighbours, and to the basement membrane beneath them, by a set of specialised junctional structures cal…

Compound epithelium is made of two or more stacked layers of cells, of which only the bottom-most layer actually rests on the basement membrane — the layers above it rest on each other.

Connective tissue is the most widely distributed tissue in the animal body. As its name suggests, it binds, supports and gives strength to other tissues and organs, holding the body's parts together a…

Loose connective tissue, part of connective tissue proper, has a matrix that is semisolid, jelly-like and viscous, built mainly from gelatin.

Areolar tissue (from areola, meaning small air pockets/spaces) is a loose connective tissue whose matrix contains two kinds of fibre: - White fibres, made of collagen, which give the tissue tensile st…

Adipose tissue (adipo = fat) is a loose connective tissue in which large numbers of rounded to polygonal fat-storing cells, adipocytes, are packed together.

Dense connective tissue has its fibres and fibroblasts packed compactly together, unlike the loose arrangement of areolar tissue. Two kinds are recognised:

Cartilage is a member of the supporting connective tissue group, characterised by a matrix that is hard yet, unlike bone, still somewhat pliable.

Bone is the other member of the supporting connective tissue group, distinguished by a hard matrix called ossein, which is built from the mineral salt hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂).

Fluid connective tissue (Vascular) consists of blood and lymph, the two fluid connective tissues found circulating through the body of an animal.

Muscular tissue is made of elongated cells called muscle fibres. Each fibre is enclosed by a cell membrane called the sarcolemma, and its cytoplasm is called the sarcoplasm.

Skeletal muscles are the muscles attached to the bones of the skeleton. A skeletal muscle is built from a large number of bundles called fasciculi, each wrapped in a connective-tissue sheath called th…

Smooth or non-striated muscles occur in the form of sheets or layers rather than as discrete bundles. Each muscle cell is spindle-shaped (fusiform), unbranched, and carries a single nucleus at its cen…

Cardiac muscle shows a mix of features found in both striated and non-striated muscle. Its sarcolemma is not distinctly visible, so although each fibre is actually uninucleate, the tissue can appear m…

Skeletal muscles can also be classified into red and white muscle, based on how much of a particular red pigment they contain.

Nervous tissue is made up of two kinds of cell: neurons (nerve cells), and neuroglia. The neuron is the structural and functional unit of the nervous system — it is the cell specialised for generating…

Based on the direction in which they carry impulses, neurons are classified into three functional types:

Neurons can also be classified by whether their axon carries a myelin sheath or not:

Based on the number of cytoplasmic processes given off from the cyton, neurons are classified into three structural types: