The Integumentary System Anatomy & Physiology Chapter 4

Classification of Body Membranes EpithelialConnective Tissue 1. cutaneous membranes ◦ skin 2. mucous membranes ◦ covers body cavities that open to exterior ◦ mucosa 3. serous membranes ◦ serosa ◦ covers ventral cavities & organs in them ◦ visceral & parietal peritoneum 1. synovial membrane ◦ no epithelial cells ◦ made of areolar CT ◦ line capsules surrounding synovial joints, tendon sheaths & bursae

 Includes: ◦ Skin ◦ Nails ◦ Hair ◦ Sweat & Oil Glands Integumentary System

Functions:  protection  body temperature homeostasis  excretion of urea& uric acid  part of vitamin D synthesis Integumentary System

 of deep tissues from mechanical damage ◦ physical barrier by keratin (toughens skin) ◦ contains pressure receptors: send sensory message to CNS; heat & cold receptors  CNS  from chemical damage ◦ skin is relatively impermeable (keratin) ◦ contains pain receptors  CNS  from bacterial invasion ◦ skin secretions are acidic so inhibit bacterial growth; phagocytes in skin ingest invaders  from UV radiation ◦ melanin made by melanocytes in skin protects nuclei Protection

 dessication ◦ keratin & other substances provide waterproofing  body temperature homeostasis ◦ when body overheated blood flow to skin increases & some heat radiates off body, sweating ◦ when body cold less blood flows to skin, more to trunk, goose bumps Functions of Skin

 excretory function: sweat contains urea, uric acid (breakdown products of proteins)  helps in synthesis of Vitamin D ◦ sunlight on skin activates conversion of pre- vitamin D  vitamin D Functions of Skin-2

Vitamin D

 made of 2 kinds of tissues 1. Epidermis 2. Dermis Structure of the Skin

 made of stratified squamous epithelium  some keratinized, some not  avascular  Cells: ◦ Keratinocytes  majority of cells  make keratin ◦ Melanocytes ◦ Langerhans Cells  Immune System Epidermis

1. stratum basale ◦ deepest layer ◦ constantly undergoing cell division/ cells pushed upward 2. stratum spinosum 3. stratum granulosum 4. stratum lucidum (only in thick skin) ◦ clear, flatter, more keratin 5. stratum corneum (cornified = keratinized) ◦ outermost layer/ dead cells thick Epidermal Layers

 dead cells flake off steadily continually being replaced by cells gradually pushing up from the stratum basale Stratum Corneum

 pigment ◦ (yellow to brown to black)  produced by melanocytes ◦ most are in stratum basale  cells stimulated to make more melanin when skin exposed to sunlight ◦ shields DNA from damaging effects of UV radiation freckles & moles: seen where melanin concentrated in 1 spot Melanin

Freckle

 causes elastic fibers to clump  leathery skin  depresses immune system  UV radiation damages DNA  skin cancer Excessive Sun Exposure

 a strong, stretchy envelope that helps to hold the body together ◦ leather is the dermis of whatever animal it was made from  made of dense CT  2 regions: 1. Papillary 2. Reticular Dermis

 upper dermis  dermal papillae: uneven projections into lower epidermis that contain: 1. capillaries 2. pain receptors 3. touch receptors: Meissner’sCorpuscles 4. in thick skin: form ridges (fingerprints) that improve gripping ability Dermis: Papillary Layer

Dermal Papillae

 deepest skin layer  Contains: 1. sweat & oil glands, hair follicles, blood vessels 2. Pacinian corpuscles (deep touch receptors) 3. many phagocytes 4. fibers: elastic: give young skin elasticity collagen: make dermis tough& keep skin hydrated by binding to water Dermis: Reticular Layer

Reticular Layer

 Skin plays major role in maintaining homeostasis of temperature:  Overheated: ◦ Blood vessels in dermis dilate  increases blood flow to skin  heat radiates off body  Hypothermic: ◦ Blood vessels in skin constrict  decreases blood flow to skin  less heat loss thru skin Body Temperature Homeostasis

 aka bedsores  due to extended restriction of normal blood supply to skin Decubitus Ulcers

 3 pigments contribute to skin color: 1. Melanin ◦ amount & kind (yellow  black) 2. Carotene ◦ orange – yellow pigment ◦ stratum corneum & subcutaneous layers 3. Hemoglobin ◦ amount O 2 bound to it in RBCs in dermal blood vessels ◦ has greater affect in light skinned people Skin Color

 cyanosis : blue hue to skin; due to poorly oxygenated blood  erythema: redness, due to increased blood flow (infection, inflammation); burn, HT, blushing  pallor: paleness, due to emotions, anemia, low BP, decreased blood flow  jaundice: yellow; usually from liver disease (not clearing bilirubin)  hematomas: bruising (bleeding under skin) Skin Color in Sickness & in Health

 Glands:  all are exocrine glands (secrete product thru ducts)  secrete their product to skin  2 groups: 1. Sebaceous glands 2. Sweat glands Appendages of the Skin

 are oil glands  all over skin except palms& soles  ducts mostly empty onto hair follicle rest onto skin surface Sebaceous Glands

 sebum: product secreted by sebaceous gland ◦ made of oils & fragmented cells and antibacterials ◦ function: lubricant’ keeps skin soft & keeps hair from getting brittle ◦ increase activity during puberty (reason skin becomes oilier) Sebaceous Glands

 if ducts become blocked  whitehead forms  material in it oxidizes & dries  blackhead  Acne: active infection of sebaceous glands, mild to severe causing permanent scarring  Seborrhea: cradle cap; overactivity of sebaceous glands  pink raised lesions  yellow to brown crust Sebaceous Glands Gone Bad

SEBACEOUS GLANDS ACNESEBORRHEA

 also known as sudoriferous glands  all over skin  2 types: 1. Eccrine sweat glands 2. Apocrine sweat glands Sweat Glands

 all over body  produce sweat ◦ clear ◦ pH 4 – 6 (being acidic  bacteriostatic) ◦ mainly water (+ NaCl, NH 3, urea, uric acid, & lactic acid) Eccrine Sweat Glands

Eccrine Glands

 typically sweat released from duct thru pore (different from facial “pores”; those are openings of hair follicles) Eccrine Glands

 important part of body’s heat-regulating equipment  + nerve endings to cause sweat to be released whenever external temperature or body temperature is high  when water in sweat evaporates it cools body  important to keep body temperature w/in few degrees of 37 ◦C or it malfunctions Eccrine Sweat Glands

 mostly in axilla & genital areas  ducts empty onto hair follicles  secretions: fatty acids, proteins, +what is in eccrine sweat  if colonized with bacteria will have odor, otherwise odorless  begin to function during puberty (stimulated by androgens) Apocrine Sweat Glands

Appocrine Glands