Histology Level 1 Semester 1 PDF

Histology lecture (13) skin (1) Histology Non-hairy Hairy Found in palms and sole Covers the rest of body Stratified squamous keratinized...

Histology lecture (13) skin (1) Histology Non-hairy Hairy Found in palms and sole Covers the rest of body Stratified squamous keratinized Connective tissue epithelium It is the subcutaneous adipose tissue. It is not a part of the skin. Histology 1. keratinocytes (85% of cells). 3. Langerhans cells. 2. Melanocytes. 4. Merkel cells. I 1- Malpighian layer (2 layers): a. Basal cell layer. b. Prickle cell layer (Stratum Spinosum). 2- Granular layer (Stratum Granulosum). 3- Clear layer (Stratum Lucidum). 4- Horny layer (Stratum Corneum). Histology  Number: Single layer of columnar cells.  Nucleus: basal & oval.  Cytoplasm: deep basophilic& (due to ribosomes).  EM: It contains prekeratin filaments.  Function: Responsible for regeneration of keratinocytes so it shows mitotic figures.  LM: Formed of 4-8 cell layers  Shape: polyhedral.  Nuclei: Central and rounded.  Cytoplasm: pale basophilic.  EM: desmosome.  The cells are connected by cytoplasmic processes.  Shape: 2- 4 layers of flattened, diamond-shaped cells.  Nuclei: flat & central.  Cytoplasm: contain 2 types of granules: Basophilic Keratohyaline-granules. Lamellar granules, which contain phospholipids, seen by EM  Function: The granules are released in the intercellular space to act as skin barrier because they are: A. waterproofing skin. a. B. preventing foreign bodies from penetrating skin.  Thin, wavy, clear, homogenous acidophilic line.  Formed of dead non-nucleated flattened cells, “scales” which contain “eleidin granules” (derivative of keratohyaline granules).  It consists of several layers of acidophilic horny scales called “squames”  The scales contain soft keratin (derived from eleidin).  The squames are continuously shed or sloughed from the surface and continuously replaced by new ones from the deeper cells. Histology II  Between the cells of the basal layer of epidermis.  Branched cells with rounded cell bodies  Rounded and central  Contains melanin pigment (brown to black pigment, responsible for pigmentation of the skin).  Synthesis of melanin III  Upper layers of the Prickle cell layer.  Blood monocytes.  Branched  Central.  Silver& vital stains.  Phagocytic& antigen presenting cells (APC). Histology IV  Basal cell layer of epidermis.  Receptors for touch sensation. Histology Thin superficial layer The thicker deep layer Formed of Loose C.T. Formed of dense C.T. More cellular Less cellular More vascular Less vascular Papillary: it Forms dermal papillae Reticular: because of its content of interlacing coarse collagenous fibers forming a "network". Receptors Pacinian corpuscles Meissner Krause end bulbs corpuscles Ruffini corpuscles Histology Palms, soles, tips of fingers and toes. whole body except site of thick skin Thick Thinner 4-8 layers 2-4 layers 2-4 layers Thinner (one discontinuous layer). Present absent Thicker with ridges and grooves on its Thinner with NO ridges and surface (finger prints) grooves on its surface (finger prints) Regular Irregular, fewer and narrower More numerous Less numerous Absent Present Absent Present Absent Present