DERMIS (CORIUM) -
- Mesodermal in origin. More developed part.
- Leather is obtained from dermis by tanning. Thinnest in eye lid. Connective tissue present.
- In it 4 types of cell are present -
(i) Fibroblast or fibrocyte - forms fibres attached to fibres.
(ii) Histocytes - Amoeba like, phagocytic in nature.
(iii) Plasma cells - formation of antibodies (g-globuline)
(iv) Mast cells - It forms matrix, heparine & serotonine.
- Collagen & elastin fibres are present.
- When elasticity of dermis is lost skin becomes wrinkeled.
- Dermis consists of b.v., lymph, vessels, unstripped muscles, nerves etc.
- Sensory papillae present in dermis (not in epidermis to avoid unnecessary stimulation).
- These papillae are of following types -
(i) Genital corpusulses - On tip of penis & clitoris.
(ii) Vater pecinian corpusulses or baroreceptor - For pressure deeply placed. More in palm & sole.
(iii) Frigido receptor or end bulb of krausi - For cold.
(iv) Allgesi receptor - For pain. Attached to free nerve endings mainly.
(v) Endings of Ruffini or Calore receptor - For hot.
(vi) Tectile corpuscles or missnner's corpuscles or markle's disc - For touch. Markel's disc is diffterent from other in structure.
(vii) Vibreo receptor - For vibration. Basal part of dermis is peniculus adiposa present on hypodermis (not a part of skin). Fat is stored in it. Also helpfull in temp. regulation. This part is absent in eye lid, prepuce & scrotal sac.
- Outer part of dermis is papillary part or pars papillaris in it dermal papullae present, fibres are dense, lines of langerhanse can be seen.
- Inner part is reticulate part or pors reticularis, papullae are absent, fibres are scattered.
- In dermis melanophage cells engulf melanin by phagocytosis.
- In some area of dermis blood passes from artery to vein directly by shunt or arterioveinuous anastamoses.