gen zoo

• Body membranes


  Line or cover, protect, and lubricate body surfaces
• Skin


  • As the outermost boundary of the body, it protects against injuries of many types
• Body membrane types


  • Epithelial membranes (cutaneous, mucous, serous)
  • Connective tissue membranes (synovial)
• Epithelial membranes


  Contain an epithelial sheet combined with an underlying layer of connective tissue
• Cutaneous membrane


  The skin, composed of a superficial epidermis (keratinizing stratified squamous epithelium) and an underlying dermis (mostly dense connective tissue)
• Mucous membrane


  Composed of epithelium resting on a loose connective tissue membrane (lamina propria), lining body cavities open to the exterior
• Serous membrane


  Composed of a layer of simple squamous epithelium resting on a thin layer of areolar connective tissue, lining closed body cavities
• Synovial membrane


  Composed of soft areolar connective tissue, lining the fibrous capsules surrounding joints
• Serous membranes occur in pairs - the parietal layer lines the wall of the ventral body cavity, and the visceral layer covers the outside of the organs in that cavity
• Serous fluid allows the organs to slide easily across the cavity walls and one another without friction
• The specific names of the serous membranes depend on their locations - the peritoneum lines the abdominal cavity, the pleura surrounds the lungs, and the pericardium surrounds the heart
• Synovial membranes also line small sacs of connective tissue called bursae and the tubelike tendon sheaths
• Synovial membranes provide a smooth surface and secrete a lubricating fluid
• Epidermis


  • Avascular - has no blood supply of its own
  • Most cells are keratinocytes which produce keratin
• Stratum basale


  Deepest cell layer of the epidermis, lies closest to the dermis and is connected to it along a wavy borderline
• Stratum spinosum


  Cells become flatter and increasingly full of keratin as they move away from the dermis
• Stratum granulosum


  Cells are flattened, organelles are deteriorating, cytoplasm full of granules
• Stratum lucidum


  Clear layer, only found in thick skin on palms and soles
• Stratum corneum


  Outermost layer, 20-30 cell layers thick, accounts for 3/4 of epidermal thickness, contains dead cornified cells filled with keratin
• Melanin


  Pigment produced by melanocytes in the stratum basale, ranges in color from yellow to brown to black, protects DNA from UV radiation
• Epidermal dendritic cells


  Important in alerting and activating immune system cells
• Merkel cells


  Associated with sensory nerve endings, serve as touch receptors
• Dermis


  Strong, stretchy envelope that helps bind the body together, consists of papillary and reticular layers
• Papillary layer


  Upper dermal region with projections called dermal papillae that indent the epidermis
• Reticular layer


  Deepest skin layer, contains irregularly arranged connective tissue fibers, blood vessels, glands, and pressure receptors
• Collagen fibers


  Responsible for the toughness of the dermis, attract and bind water to keep skin hydrated
• Elastic fibers


  Give the skin its elasticity when young, decrease with age leading to sagging and wrinkling
• Skin color


  Determined by melanin, carotene, and hemoglobin in blood vessels
• Emotions and diseases can influence skin color changes like redness, pallor, jaundice, and bruising
• Skin appendages


  Include cutaneous glands, hair and hair follicles, and nails
• Cutaneous glands


  Exocrine glands that release secretions to the skin surface via ducts, include sebaceous and sweat glands
• Sebaceous glands can make hair lank and oily
• The skin appendages include cutaneous glands, hair and hair follicles, and nails
• The cutaneous glands are all exocrine glands that release their secretions to the skin surface via ducts
• Types of cutaneous glands

  • Sebaceous glands
  • Sweat glands
• Sebaceous (oil) glands


  Glands found all over the skin, except on the palms of the hands and the soles of the feet, that produce sebum - a mixture of oily substances and fragmented cells that lubricates the skin and hair
• Sebaceous glands become very active

  When male sex hormones are produced in increased amounts (in both sexes) during adolescence
• Sweat glands


  Also called sudoriferous glands, they are widely distributed in the skin with over 2.5 million per person. They produce sweat, a clear secretion that is primarily water plus some salts, vitamin C, traces of metabolic wastes, and lactic acid.
• Eccrine sweat glands


  • They are an important and highly efficient part of the body's heat-regulating equipment, secreting sweat when the external or body temperature is high to help cool the body through evaporation
• Apocrine glands


  Larger than eccrine glands, they are largely confined to the axillary (armpit) and genital areas. Their secretion contains fatty acids and proteins and may have a milky or yellowish color. It is odorless but can take on a musky, unpleasant odor when bacteria use it as a nutrient source.