The Integumentary System “The Skin” - Anatomy Notes
Sheet-like structures Membranes Sheet-like structures Cover and protect body surfaces Secrete fluid for lubrication
Epithelial Membranes Cutaneous – skin Serous – lines body cavity & covers surface of organs Pleura – thoracic cavity Peritoneum – abdominal cavity Mucous – line surfaces (openings) Secrete slimy mucus keeps membranes moist and soft
The Skin Did you know? – Draw a 1 inch square on your paper… 1 square inch of skin contains… 500 sweat glands 1000 nerve endings yards of vessels 100 oil glands 150 pressure sensors 75 heat sensors 10 cold sensors millions of cells The whole organ makes up 16% of a person’s body weight
Layers of the Skin Epidermis (thin, outer layer) – layers of tissue Superficial layers (keratinized cells – dry, dead) flake off Deep layers = rapidly dividing cells (move toward surface) Cytoplasm replaced by keratin – tough, waterproof protein Deepest layers produce pigments Melanin (melanocytes) – genetics/sun exposure Areas with little melanin used to indicate blood flow (nails/lips) flushed (normal) blue (decrease blood flow) – cyanosis
Epidermis
Layers of the skin Dermis (deep, thick layer) – cells scattered with fibers Upper portion forms ridges/grooves – fingerprints Lower portion contains collagen (strength), elastic fibers, & nerve endings – amount decreases with age
Dermis
Appendages Hair – protection/warmth Erector Pili muscles – goose bumps
Appendages Receptors (touch, pain, pressure, temp.) Sensation becomes part of our awareness when transmitted to brain where info can be… Amplified Reduced Eliminated
Appendages Nails Protection (hard, plate-like, keratinized cells)
Appendages Sweat (sudoriferous) Glands Eccrine gland – watery Perspiration (eliminate waste, temp. control) Apocrine gland – thick, milky Armpit/groin (smell (BO) – bacteria)
Appendages Sebaceous Glands – secrete oil for hair/skin Sebum – lubrication (prevents drying/cracking)
The Skin