Integumentary System - Skin Chapter PDF

Chapter 5 INTEGUMENTARY SYSTEM Integument  Skin  Glands  Hair  Nails Functions  Protection  Sensation  Temperature regulation  Vitamin D production  Excretion Protection  Skin-  From mechanical damage like abrasion and tearing of skin...

Chapter 5 INTEGUMENTARY SYSTEM Integument  Skin  Glands  Hair  Nails Functions  Protection  Sensation  Temperature regulation  Vitamin D production  Excretion Protection  Skin-  From mechanical damage like abrasion and tearing of skin  Barrier and defense of microorganisms/water loss  UV light absorption to protect underlying structures  Hair- insulator and trap particles  Nails- defense Sensation  Receptors detect heat, cold, pain, pressure Temperature Regulation  Blood vessels in the Dermis dilate and bring warm blood to the surface and heat loss increases *increase in sweating also lets off warmth  Blood vessels in the Dermis constrict which causes less warm blood to the surface and keeps the core warmer *shivering adds warmth Heat Loss Heat Conservation Vitamin D Production  Vitamin D is needed for Calcium and Phosphate absorption in the small intestine  A precursor molecule to Vitamin D is found in the skin and when it is exposed to UV light, it gets converted to cholecalciferol and then to calcitriol(Vitamin D) by the kidneys and liver  (Vitamin D can be found in liver, egg yolks, and dairy) Vitamin Synthesis Excretion  Urea, uric acid, ammonia wastes are excreted in sweat Skin  Epidermis- Superficial layer - Stratified Squamous Epithelium  Dermis- Deep layer - Loose-Areolar CT - Dense Irregular CT  Hypodermis/Subcutaneous - Below dermis - Adipose CT - Loose CT Epidermis  Stratified squamous epithelial tissue  Basement membrane and apical surface  Nourishment from dermis (no blood vessels)  Cells: - keratinocytes- produce protein keratin to harden cells to resist abrasion and reduce water loss - melanocytes-produce pigment melanin for skin color - langerhans cells-immune cells - merkel cells- nerve endings for light touch sensation Epidermis Epidermis  Mitosis at basement membrane  Desquamate at surface  Keratinization- stem cells in basal layer and undergo mitosis and push towards surface. As move upward undergo changes in shape and gather keratin through the layers of epidermis and become hardened and eventually die and slough off. Strata of Epidermis  Stratum Basale  Stratum Spinosum  Stratum Granulosum  Stratum Lucidum  Stratum Corneum Strata Stratum Basale Structures:  deepest layer and attaches to underlying dermis  1 layer of cuboidal or columnar cells  Cells are Keratinocytes or melanocytes Functions:  divides pushed up to be keratinized  divides every 19 days  40-56 days to desquamate Stratum Spinosum Structures:  8-10 layers  flatten toward surface and break attachment of desmosomes  Reattach by new desmosomes and cells shrink and look spiny Function:  Keratinization Stratum Granulosum Structures:  2-5 layers of flattened/diamond shaped cells  protein granules called keratohyalin Function:  Keratinization and cells dying Stratum Lucidum Structures:  several dead layers  Clear appearance  keratin fibers present but keratohyalin disperses Function:  Disperse keratohyalin  Thick skin UV layer Stratum corneum Structures:  superficial layer of squamous cells  25 or greater dead layers  cornified cells- dead/hard keratinized cells  slough off Functions:  Structural strength  Water loss prevention  Resist abrasion Thick Skin- 5 layers of epidermis Locations:  Areas with pressure/friction  Palms  Soles  Finger tips  Callus- extra build up of corneum layers due to friction  Corn- extra build up of corneum over a bony prominence Thin skin- 4 layers Locations:  Most of body  Areas with hair  Less layers and generally no lucidum Skin Color Factors that effect skin color:  Melanin pigment  Blood flow  Thickness of stratum corneum Melanin  Melanocytes produce melanin  Melanin then transferred into the keratinocytes and evenly distributed Functions:  Skin/eye/hair color  Freckles/areola/moles/axilla/genitalia  None or less in the lips/palms/soles  UV protection  Determined by genetics/sun/hormones melanocytes Changes in skin color  Albinism- no melanin  Tanning- increased production of melanin due to UV exposure  Pregnancy- increased melanin due to hormones  Erythema- blood under the epidermis changing its color to reddish  Cyanosis- lack of blood under epidermis making it bluish  Carotene- yellow pigment in plants consumed in excess Dermis  Connective tissue- 2 layers (papillary/ reticular) Structures:  Cells – Fibroblasts/ Adipose cells/ Macrophages  Matrix- mostly collagen fibers/ some elastic and reticular fibers  Blood and lymph vessels  nerve endings  Hair follicles  Smooth muscles  Glands Dermis Structures Dermis  1. Papillary layer- superficial - loose CT (Areolar) - blood vessels/nerve endings Function: - dermal papillae- in thick skin impress into the epidermis making unique pattern called friction ridges or finger prints Dermal papilla Dermis  2. Reticular Layer- deepest - Dense Irregular Collagenous Connective Tissue - Hair follicles/nerve endings/blood vessels Functions: - resist stretch - elastin/collagen fibers in cleavage lines(tension lines) - striae- stretch marks- over stretching or tearing of fibers in dermis Cleavage Lines Hypodermis  Attaches skin to underlying structures  Loose Connective Tissue (adipose mostly)  Cells- adipocytes/fibroblasts/macrophages  Matrix- Collagen/elastin fibers - Blood vessels and nerves  Functions: - storage energy - insulation - padding Hypodermis Injections Hair 3 types:  Lanugo- unpigmented hair of a fetus  Terminal hairs- scalp/eyelashes/eyebrows  Vellus hairs- hair on arms and legs - at puberty, terminal hairs replace vellus hair in axilla/pubic region/beard Hair Types  Lanugo  Vellus  Terminal Hair Structure Structures:  Shaft- above the surface  Root- below the skin surface  Bulb- base of the root  Medulla- middle axis of the hair with soft keratin  Cortex- outside of medulla and bulk of the hair with hard keratin  Cuticle- outside covering  Follicle- invagination of the epidermis into the dermis where the hair resides Hair Hair characteristics  Hair growth- begins at base of root (bulb).  Can lose 100 hairs/day and new ones start growing in their place - alopecia  Color - melanin (into keratinocytes like the skin) - blond/black/brown/red/gray Arrector Pili Muscle  Arrector pili muscles- smooth muscle attached to the hair follicle that contract in response to cold/emotional response and makes hair stand on end (goose bumps) Glands  Oil- Sebaceous  Sweat- Sudoriferous  Ear wax- Ceruminous Sebaceous Glands-Oil  Located in dermis  Produce sebum (oil) - ducts connect to surface - often through a hair follicle  Holocrine glands  Function- sebum prevents drying of skin and protects against bacteria Sudoriferous Glands- sweat 1. Merocrine (Eccrine) - open on skin thru coiled pore - sweat= water/salts/ammonia/urea/uric acid - released when: increased body temp. or emotional stress(axillae/palms/soles) Sudoriferous Glands- sweat 2. Apocrine - open into hair follicles - axillae/genitalia - released when: sexual hormone triggered - odorless until mixed with bacteria Other glands  Ceruminous - modified merocrine - ear canal - cerumen (ear wax)- combo ceruminous and sebaceous glands) - prevent dirt and insect from getting deep in canal  Mammary - modified apocrine sweat glands - milk production Nails  Dead stratum corneum with hard keratin  Functions: - protect digits - grasp - scratching  Structures: - Root- proximal - Body- distal - Fold- sides of skin - Eponychium- cuticle - Hyponychium- under free edge - Free edge- distal tip - Bed- deep to the body - lunula- white crescent shape