Tough protective, external covering of the body that is continuous with the mucosa that lines the mouth, nose, anal canal, genital openings and eyes
Skin
Semi-permeable membrane that can absorb certain substances from its surface
Epidermis
The more superficial layer; it is an epithelial coat derived from ectoderm
Dermis (corium)
Made up of connective tissue derived from mesoderm
Tissue elements of the dermis form irregular conical projections called dermal papillae
Anchored to the underlying tissues by loose connective tissue that is referred to as hypodermis or subcutaneous tissue that often contains numerous adipose cells
Epidermis
Keratinized stratified squamous epithelium
Most superficial layer is continuously shed and is completely renewed every 20 to 30 days
Keratinocytes
Responsible for the renewal process due to its production of keratin
Layers of thick skin
Stratum basale (Stratum germinativum)
Stratum spinosum (Prickle cell layer)
Stratum granulosum
Stratum lucidum (Clear layer)
Stratum Corneum (Horny cell layer)
Layers of thin skin
Stratum spinosum and stratum corneum is thinner
Stratum granulosum is poorly developed and sometimes even absent
No stratum lucidum
Melanocytes
Cells that are specialized to produce melanin pigment
Skin color pigments
Carotene
Hemoglobin
Melanin
Langerhans Cells
Myelold-related dendritic cells
Antigen-presenting cells
Most numerous in the stratum spinosum
Contain rod-shaped, membrane-bound granules called Birbeck granules or vermiform granules
Merkel cells
Least in number among the cell types in the epidermis
Disk shaped cells with short cytoplasmic processes
Supplied with an axon termination of a sensory neuron that penetrates the basal lamina
The axon termination of and the merkel cell forms Merkel disc- a sensory mechanical receptor that responds to pressure and touch
Papillary layer
Made up of loose connective tissue that compromises that papillary layer form conical projections into the epidermis called dermal papillae
Reticular layer
Responsible for the toughness and strength of skin
Consist of dense irregular connective tissue that is richly supplied with blood vessels and whose collagen fibers form coarse bundles that are most oriented parallel to the skin
Sweat glands, sebaceous glands and hair follicles, when present, are embedded in the connective tissue of the reticular layer
Hypodermis (Subcutaneous tissue)
Refers to the loose connective tissue that binds the dermis of the skin to the underlying structures
It allows the skin to slide over the underlying structures
Nerve Endings in Skin
To receive sensory stimuli and transmit the same to the central nervous system that regulate the activity of its glands and smooth muscle cells, including those in blood vessels
Hair
Is a filamentous, keratinized structure that covers practically the whole body
Hair has hardly any protective function but is still important to the sense of touch
The part afa hair that, projects from the surface of the skin while the part that is embedded in the skin is called root
Hair follicle is the point from which the hair grows
The part of the hair seen above the skin is called the hair shaft
Layers of hair shaft
Medulla
Cortex
Cuticle
Nail
Protects the ends of your fingers and toes
Nail plate: The hard part of your nail you can see
Nail bed: The skin under your nail plate
Cuticle: The thin skin at the base of your nail plate
Matrix: The "root" of your nail responsible for making it grow
Lunula: The white, moon-shaped part of your nail plate