Dr. ANAND SRINIVASAN

 Able to :  Describe, identify and draw the histological features of structures forming the integumentary system

 It includes  Skin  Hair  Nails  Heaviest organ of body – 1/6 of total body wt.  Surface area – 18 sq. ft

 On close observation of skin  Tension lines – due to anchoring fibrils of dermis  Flexure lines – joints  Papillary ridges – over palm & sole; unique for each individual  Dermatoglyphics – study of finger prints

 Protection  Sensation  Thermoregulation  Synthesis of Vitamin D  Excretion  BP regulation  Storage  Absorption

 THIN SKIN  Thin Epidermis  Presence of Hair  All parts – EXCEPT Palm & Sole  THICK SKIN  Thick epidermis (Thick stratum corneum)  No Hair  Palm & Sole

 Made of 2 layers – Epidermis & dermis  Dermo – epidermal junction is uneven – has ridges (epidermal ridges & dermal papillae) where they can interlock with each other.

 Made of stratified squamous keratinized epithelium  Projects into dermis – Epidermal ridges  Avascular & nourished by diffusion  Renewed every 15 – 30 days depending of region of body, age etc

 STRATUM BASALE  Deepest layer with single layer of cuboidal / low columnar cells  STRATUM SPINOSUM  Polyhedral cells held together by desmosomes  Tonofilaments  STRATUM GRANULOSUM  3 – 5 flattened fusiform cells  Filled with keratohyalin granules (precursor of keratin)  Membrane coating granules (sealing effect)  STRATUM LUCIDUM  Flat eosinophilic dead cells forming homogenously glassy layer  STRATUM CORNEUM  Most superficial layer of epidermis  Flattened non nucleated dead

 KERATINOCYTES (90%)  Present in all 5 layers  MELANOCYTES  Present in basal layer as clear cells  LANGERHANS CELLS  Mainly in stratum spinosum  MERKEL’S CELLS  Present in stratum basale

 Made of vascular connective tissue  2 layers  Papillary layer  Reticular layer ▪ Contains hair follicles, sweat glands, receptors

 Holocrine gland  Found in the dermis  Simple acinar duct opening into hair follicle  CLINICAL CORRELATES  Acne, Sebaceous cyst

 Absent in Glans penis, inner surface of prepuce and margins of lip  Simple, coiled, tubular gland  2 types of sweat glands  Merocrine & Apocrine

 Made of cuticle, cortex and medulla

 Cornified plate of stratum corneum  Eponychium & Hyponychium EPONYCHIUM HYPONYCHIUM

 Wheater’s Functional Histology  Cell Biology & Histology – Board Review Series  Microanatomy workbook – RAKMHSU