In this article we will discuss about:- 1. Integument in Mammals 2. Horns in Mammals 3. Antlers.
Integument in Mammals:
Epidermis is divided into five layers; from outside these are as follows (Fig. 2.20):
(i) Stratum corneum:
ADVERTISEMENTS:
This is the outermost keratin layer. Cell boundary is indistinguishable and nucleus is absent. This layer is thick in the palm and sole and thin in the lips. Hair developed from this layer.
(ii) Stratum lucidum:
This is the second layer from the outside. It is a thin layer. Cells are devoid of nucleus and cell membrane is inconspicuous. The cells of this layer possess eleidin which gives rise to keratin.
(iii) Stratum granulosum:
ADVERTISEMENTS:
Third layer from the outside and is composed of three to five cell layers. The cells contain keratohyaline granules, responsible for the name of the layer.
(iv) Stratum spinosum:
This is fourth layer from the outside. It is much thicker than the others. The cells of this layer bear several spiny structures emerging out from the membrane. So these are called prickle cells. These spines attach with the spines of the adjacent cells.
(v) Stratum basale:
ADVERTISEMENTS:
This is the fifth and last layer of the epidermis. The cells of this layer are columnar and continuously dividing mitotically to replace upper layers. Cytoplasmic extensions from the basal cells reach the cells of dermis.
(vi) Stratum Malpighi:
This layer is not the part of epidermis. But present in-between epidermis and dermis. This layer possesses branched cells called melanocytes. Dermis or Cutis vera is composed of collagenous and elastic fibres. Upper layer of dermis is well-organised papillary layer, which maintains connection with the melanocytes and prickle cells.
Inner layer of dermis is loose connective tissue with fat deposition. Fibroblast cells of the dermis produce fibrous tissue and reticulo-endothelial system. Some of the cells possess melanin pigment and are called melanophore. Dermis contains sweat, ceruminus, and sebaceous gland