Membranes and the integumentary system

mmm skin

Purpose of the body membrane

Purpose of the body membrane

surrounds and protects various surfaces of the body

list the various surfaces of the body

external and internal cavities, synovial joint capsules, the skin

Epithelial membrane function

One of the main groups of body membrane (epithelial and connective tissue membranes), acts as a lining for both internal and external body surfaces

what do epithelial membranes consist of

a sheet of epithelial cells and a layer of connective tissue, there are multiple types of epithelial membranes, mucous, serous and cutaneous

Mucous membranes function

line body cavities that open up to the outside world, one type of epithelial membrane. The respiratory, digestive, urinary and reproductive tracts are lined with mucous membranes. Moist and secrete mucus for protection and substance transport

what do mucous membranes structure

layer of epithelium on top of a layer of connective tissue called lamina propria

serous membrane function

lines closed body cavities like the pleura (covers the lungs), pericardium (encloses the heart and major blood vessels) and perioneum (lines the abdominal cavity). Secretes serous fluid, lubricates cavities, reduces friction and protects moving organs

serous membrane structure

forms double lining. Parietal layer (outer lining of cavity), visceral layer (inner lining covering organs) Outer layer of simple squamous epithelium on a thin layer of loose connective tissue

cutaneous membrane function

refers to skin, has a structure of keratinizing, stratified squamous epithelium, over dense, fibrous connective tissue. considered a dry membrane when sweat is not present, although does contain sweat glands

connective tissue membranes

these membranes encapsulate organs and line movable joints, an example is synovial joints

Synovial membrane function

a connective tissue membrane that does not include epithelial cells, synovial membranes line the capsules around synovial joints, tendon sheaths and bursae. Secretes synovial fluid, cushions and reduces friction in moving structures

Integumentary system consists of

the skin, sweat and oil glands, nails and hair

Integumentary system functions

Protective layer for underlying tissues, defends against injuries. Keratin in skin provides structural strength and protects against chemicals. Skin functions as a water barrier, prevents excessive evaporation and water entry. Regulation of body temperature is achieved through capillaries and sweat glands in the skin. Skin produces melanin which protects against UV radiation and synthesizes vitamin D. Chemical waste products eliminated through sweat, helps protect against infections. Cutaneous sensory receptors in skin transmit information about touch, pressure, pain and temperature.

anatomy of the skin

composed of 2 layers: outer epidermis and underlying dermis. Epidermis and dermis can vary in thickness in different areas of the body. Below dermis is hypodermis - stores fat and connects skin to underlying tissues, cushions and insulated. Contains specialized cutaneous sensory receptors, part of the nervous system

Structure of epidermis

consists of 5 layers: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum and stratum Basale. Epidermal layers don’t receive blood supply, instead receive nutrients from dermis, primarily through stratum Basale. Cells in stratum Basale continuously produce new skin cells, gradually move towards surface and eventually die.

Majority of cells in epidermis are keratinocytes, which produce keratin. Cells in stratum spinosum and granulosum become flatter and more filled with keratin, making them tough and water resistant.

Stratum lucidum is a clear layer found in thick skin areas like pals, soles and fingers. Stratum corneum consists of dead cells filled with keratin - continuously shed. Epidermis completely regenerates every 25 - 45 days.

cells in epidermis

Stratum basale contains melanocytes, sunlight exposure stimulates melanin production, resulting in tanning and increased sun production.

Epidermal dendritic cells - initiate immune responses to pathogens

Merkel cells - in stratum basale serve as touch receptors and transmit sensory information to the brain.

anatomy of dermis

Dermis is dense and fibrous, composed of collagen and elastic fibers.

collagen fibers give toughness and bind with water to maintain skin moisture

elastic fibers prevent wrinkles and sagging (aging = decrease in collagen and elastic fibers)

Dermis has rich blood supply, aiding in heat regulation

Specialized sensory receptors for touch, vibration, pain and temperature are present in the dermis

Phagocytes in the dermis ingest foreign materials and dead cells

papillary layer

the outer layer of the dermis (still part of the dermis), contains dermal papillae with capillaries and nerve endings. Dermal papillae for unique patterns on palms, fingers, toes and soles, forming fingerprints

reticular layer

beneath the papillary layer (rest of the dermis) and as irregular arrangement of collagen and elastic fibers. Contains blood and lymphatic vessels, sweat and oil glands, muscles, hair follicles and nerve endings

Hypodermis

consists of fibrous connective tissue and adipose tissue. Fat cells are present in the hypodermis, providing padding, insulation and energy storage

Appendages of the skin: sudoriferous glands (sweat glands)

found throughout the dermis - higher concentration under the arms, on the palms, soles and forehead. two types: eccrine and apocrine glands

Eccrine glands

the major sweat glands, covers most of the body and opening directly onto the skin.

sweat from eccrine glands is clear and watery, containing water, urea, uric acid, salts and vitamin C

Bacteria chemically changes sweat on the skin - results in odor

nerve endings in sweat glands stimulate sweat production in response to increased body or external temperature

evaporation of sweat helps dissipate body heat

apocrine glands

larger than eccrine glands and primarily found in genital and armpit areas

secrete milky fluid containing sweat, fatty acids and proteins

unlike eccrine gland ducts, apocrine gland ducts empty into hair follicles

Appendages of skin: sebaceous glands

found throughout body, except for palms and soles.

produce oily substance - sebum

Most sebaceous glands empty into hair follicles, some directly onto skin

keeps skin and hair soft, also has chemicals with antibacterial properties

sebaceous glands more active during adolescence - oily skin for teens

appendages of skin: hair

hair follicles: structures within dermis that produce hair

base of follicle contains papilla of connective tissue with a rich capillary supply for nourishment

specialized cells in follicle growth zone (matrix) divide and generate living hair cells, as they move upward, they fill with keratin and become non-living

hair shaft is mostly protein

hair color and texture determined by melanocytes within hair follicle, reduced pigmentation = white/ grey hair with aging

shape of hair follicle determines texture (straight, wavy etc)

arrestor pili muscles connect hair follicle to dermis, once stimulated, cause hair to stand upright - goosebumps, traps air close to skin for insulation and warmth

appendages of skin: nails

nail bed is a specialized region of the stratum basale underlying each nail

nail matrix, located at proximal end of nail bed is responsible for nail growth

nail growth occurs in the matrix as new cells rapidly become keratinized and die

nails are transparent by appear pinkish due to capillary supply beneath stratum basale

the white, crescent moon shaped region at base of nail is called lunule - positioned over thickened nail matrix and has a curved shape similar to a crescent moon