Chapter 5 - Integumentary System Flashcards
Integumentary System consists of:
- Skin (aka cutaneous membrane)
- Accessory structures
- Sensory receptors
Skin (Cutaneous membrane) contains:
skin–layers of tissues;
- Epidermis - stratified squamous epithelial; avascular; top 15% of skin; outer layers are “dead cells”; heavily keratinized at surface
- dermis - CT (dense irregular); vascular; bulk of skin–80-85% of skin
Accessory structures (& examples)
structures embedded or sticking out of skin; ex. hair, nails, sebaceous glands, sweat glands
Sensory receptors (& examples)
part of nervous system;
ex. touch, pain/temp, pressure sensors
4 cells that make up Epidermis
- Keratinocyte
- Melanocyte
- Langerhans cells
- Merkel cells
Keratinocyte
most abundant (approx. 90%) cells in epidermis; found in all layers of epidermis; cell make keratin (tough outer surface)
Melanocyte
makes main skin pigments which are called melanin; protects us from UV radiation; found in deepest layer of epidermis–stratum basale
Langerhans cells
immune cells found in epidermis; defense of skin
Merkel cells
touch sensors; found in epidermis
5 Layers of Epidermis (in order–top layer to bottom layer):
- Stratum corneum - top layer
- Stratum lucidum - only present in thick skin; places we rub a lot
- Stratum granulosum - cells are dying & beginning to break down & granules are released
- Stratum spinosum - “living layer” of cells
- Stratum basale - bottom layer; most important layer
Characteristics of Stratum Corneum (Epidermis):
20-30 layers (most layers) of dead, flattened keratinocytes; keratin inside keratinocytes; protect skin, glycolipids in extracellular space waterproof
Characteristics of Stratum Lucidum (Epidermis):
few cell layers (3-5); translucent layer of dead & flattened keratinocytes; thick skin = soles of feet, palms
Characteristics of Stratum Granulosum (Epidermis):
several cell layers, granules accumulate, nuclei & organelles disintegrate in keratinocytes; some granules from keratin & some form water-protection; keratinocytes - half dead cells - dying
Characteristics of Stratum Spinosum (Epidermis):
“living layer” of cells; several cell layers of keratinocytes; keratinocytes contain intermediate filaments; some Langerhans’ cells present in cell layers
Characteristics of Stratum Basale (Epidermis):
most important layer; a SINGLE layer of actively dividing keratinocytes; also contains merkel cells & melanocytes; melanocytes–only present in bottom layer; keratinocytes are formed & divide in this layer; old keratinocytes are pushed up each layer so they get older as they move up each layer
2 Layers of Dermis (in order–top layer to bottom layer):
- Papillary layer - areolar CT; right next to epidermis; richly vascularized
- Reticular layer - dense irregular CT; poorly vascularized
Characteristics of Papillary layer (Dermis):
dermal papillae contain capillary loops, free nerve endings, Meissner’s corpuscles; supplies the epidermis; bumpy thin layer
Characteristics of Reticular layer (Dermis):
collagen arranged in different directions; contain sweat glands, Pacinian corpuscles, hair follicles, sebaceous glands; function: to hold the accessory structures
Hypodermis
layer under the skin; under the dermis; “subcutaneous layer”; mostly adipose tissue; vascularized; mainly fat cells–nutrient storage & insulation
Papillary layer (Dermis)
dermal papillae–hill or mound of CT
Capillary loops
thin blood vessels where exchanges can take place; holds Oxygen & nutrients & supplies it to epidermis; papillary layer (dermis)
Free nerve endings
pain & temp sensors; able to sense extreme temp that are likely to damage skin; papillary layer (dermis)
Meissner’s Corpuscles
touch sensors; papillary layer (dermis)
Reticular layer (Dermis)
doesn’t really help epidermis for blood supply bc further away & dense (so not many blood vessels); a lot of of accessory structures found here
Pacinian corpuscles
pressure/vibration sensors; reticular layer (dermis)
Pigments that contribute to skin color:
- Melanin - protects us from UV radiation damage; make in skin
- Carotene - comes from food; not made in body
- Hemoglobin - can show thru very light skin; if you don’t have much melanin & very light skin, hemoglobin could show through skin & skin would be “pink”
Accessory Structures:
- Sebaceous glands
- Sweat glands
- Modified sweat glands
- Nails
- Hair
Sebaceous glands
oil secreting glands; holocrine-how it secretes; cell ruptures & releases oil & cell fragments; function: to lubricate skin & hair
Sebum
secretion from sebaceous gland; oil & cell fragments
Sweat glands
99% water; coiled structures that have ducts that lead to surface; how it secretes-merocrine (exocytosis); what it secretes-Exocrine gland; function-regulates body temp
- Eccrine glands
- Apocrine glands
Eccrine glands (Sweat glands)
found all over body; stimulated by nervous system; cools down body; clear type of sweat
Apocrine glands (Sweat glands)
mainly found in armpits, genital & anus; start functioning around puberty; respond to STRESS & SEXUAL excitement; more proteins & fats in sweat & produces “smelly” type of sweat; not as abundant; more hormonally controlled; mixes w/bacteria & causes a smell
Modified Sweat Glands
don’t produce sweat; similar to sweat glands; merocrine (exocytosis)
- Ceruminous glands - only in ear canal; secretes ear wax by exocytosis
- Mammary glands - produce milk in lactating women
Nails
modified epidermis; avascular; made of epithelial cells; cells become keratinized as they are pushed to surface; CT is right next to nail matrix but as they reach surface, they are dead
Nail Root
inside skin; not visible
Nail body
part of nail visible but still attached to skin
Free Edge
visible part @ very tip but no longer attached to skin; oldest nail cells located here
Nail Matrix
consists of actively dividing nail cells; not visible; nail cells formed here
Nail Keratin
harder; doesn’t flake off
Hair
modified epidermis; epithelial cells
Hair Root
embedded in skin
Hair shaft
hair that sticks out of skin (visible)
Hair follicle
not part of hair; protective covering & helps anchor it in dermis
Hair matrix
consists of one layer of cells; cell division; all growth of hair occurs here; pushes older hair cells up to surface–where it is dead (no oxygen or nutrients); keratin forms as hair cells die off; avascular; has MELANOCYTES for hair color
Hair papilla
has blood vessels; neighboring CT; not part of hair
Hair root plexus
bunch of nerves wrapped around hair follicle; touch sensor (wind blows, etc); found in reticular layer
Arrector pili muscle
smooth muscle attached to hair follicle; contracts when we are cold or nervous; causes hair to stand up
Merkel Cell (sensor & location)
Sensor: touch
Location: epidermis
Meissner’s corpuscle (sensor & location)
Sensor: touch
Location: papillary layer
Hair Root Plexus (sensor & location)
Sensor: touch
Location: reticular layer
Free nerve ending (sensor & location)
Sensor: pain/temp
Location: papillary layer
Pacinian corpuscle (sensor & location)
Sensor: pressure
Location: reticular layer
Living cells are on bottom layer of skin & are closer to dermis; these cells get the most oxygen & nutrients
as they get closer to surface, they are too far away to get oxygen & nutrients to survive
Review pic of cross section of hair (from inner to outer layer)
- Medulla - inner layer; consists of large hair cells & air
- Cortex
- Hair
- Follicle
- Cuticle - outer layer of hair; what you see; shape of hair determines hair texture; oval like-wavy; thin - curly
