Chapter 5 Flashcards
Skin Structure Image
What does the integumentary system consist of?
Skin
Hair
Nails
Sweat Glands
Sebaceous (oil) glands
What are the distinct regions of the skin? What tissues is each made of?
Epidermis - Epithelial tissue
Dermis - Dense connective tissue
Hypodermis - adipose tissue with areolar connective tissue
What are the 4 cell types found in the epidermis? What does each do?
- Keratinocytes - protection
- Melanocytes - shields and protects the nucleus from damaging UV radiation in sunlight.
- Dendritic cells - ingest foreign substances and are activators of the immune system.
- Tactile (Merkel) cells - act as sensory receptors for touch.
What are the 5 layers of the epidermis?
Stratum corneum
Stratum lucidum (only in thick skin)
Stratum granulosum
Stratum spinosum
Stratum básale
Apoptosis
Cell death
In epidermis the cells slough off as dandruff and dander. Humans can shed 50,000 cells every minute.
Image of epidermal layers
What is dermis? What does it contain and what are its 2 layers?
Dermis is made of strong, flexible connective tissue. The dermis’ matrix fibers bond the body together. The dermis contains nerves, blood vessels and lymphatic vessels, epidermal hair follicles, oil glands, & sweat glands.
2 layers:
Papillary
Reticular
Papillary Layer
The papillary layer of the dermis is made of areolar connective tissue consisting of loose collagen, elastic fibers and blood vessels.
The loose fibers of the papillary layer allow phagocytes to patrol for microorganisms.
Dermal Papillae
The dermal papillae is a superficial region of dermis that sends fingerlike projections up into the epidermis.
Dermal papillae projections contain capillary loops, free nerve endings, and touch receptors (tactile corpuscles).
Friction Ridges - what are they made from and what do they do?
In thick skin, the dermal papillae lie on top of dermal ridges which give rise to epidermal rings. These collectively are friction ridges.
Friction ridges enhance finger’s gripping ability.
Friction ridges contribute to sense of touch.
Sweat pores in friction ridges lead to unique fingerprint patterns.
The reticular layer of dermis
The reticular layer makes up 80% of dermal thickness.
The reticular layer is made up of coarse, dense fibrous connective tissue, with elastic and collagen fibers.
The reticular layer binds water and keeps skin hydrated.
Cutaneous plexus lies in the reticular layer.
Cutaneous Plexus
The cutaneous plexus is a network of blood vessels between the reticular layer of the dermis and the hypodermis.
Flexure Lines
Flexure lines are lines of the reticular layer that are dermal folds at or near joints.
The dermis is tightly secured to deeper structures.
The skin’s inability to slide easily for joint movements causes deep creases.
Flexure lines are visible on the hands, wrists, fingers, soles & toes.
What are the 3 main skin color pigments? Which is the only one produced by the skin?
Melanin - produced by skin
Carotene
Hemoglobin
What are the functions of hair?
Hair…
Warns of insects on skin
Hair on head guards against physical trauma
Protects from heat loss
Shields the skin from sunlight
Hair structure
Hair is made up of dead keratinized cells (Hard keratin)
Hard keratin is tough, cells do not flake off.
Hair is produced by hair follicles.
Regions of hair:
The Shaft: the area that extends above the scalp, where keratinization is complete.
The Root: the area within scalp, where keratinization is still going on.
3 parts of hair shaft:
Medulla - central core of the large cells and air spaces.
Cortex - several layers of flattened cells surrounding the medulla.
Cuticle - the outer layer consisting of overlapping layers of single cells.
What are hair pigments made by? How do hair pigments work?
Hair pigments are made by melanocytes in the hair follicles.
Photo: Structure of hair follicle
Photo structure of a hair follicle
What is the wall of a hair follicle composed of?
The wall of a hair follicle is composed of:
- The peripheral connective tissue sheath.
- The glassy membrane.
- The epithelial root sheath.
Vellus hair
Pale fine body hair
Terminal hair
Coarse long hair (eyebrows, scalp, at puberty).
Nails
Nails are scale-like modifications of the epidermis that contain hard keratin.
Nails are protective covers for the fingers and toes.
Nails consist of the nail matrix, nail bed, nail folds, epoychium, hyponychium, and lunule.
Nail bed
The nail bed is the epidermis under the keratinized nail plate.
Nail matrix
The nail matrix is the thickened portion of the nail bed responsible for nail growth.
Nail folds
Nail folds are skin folds that overlap the border of nails.
Eponychium
Eponychium are nail folds that project onto the surface of the nail body (cuticle).
Hyponychium
The hyponychium is the area under the free edge of the plate that accumulates dirt.
Lunule
Lunule is the thickened nail matrix. It appears white.
Photo: structure of nail.
Sweat glands (what are the 2 main types and what cells do they contain?)
- Eccrine (merocrine) sweat glands.
- Apocrine sweat glands. Apocrine sweat glands contain myoepithelial cells - these cells contract upon the stimulation of the nervous system, forcing sweat into ducts.
Eccrine sweat glands
Eccrine sweat glands are the most numerous type of sweat glands. They appear on the palms, soles and forehead.
Eccrine sweat glands have ducts that connect to pores.
Eccrine sweat gland function: thermoregulation: regulated by the sympathetic nervous system.
Eccrine sweat gland secretion: sweat
Photo: cutaneous glands
Apocrine sweat glands
Apocrine sweat glands are confined to axillary and anogenital areas.
Apocrine sweat glands secrete viscous sweat that contains fatty substances and proteins. This sweat has no smell. It’s the bacteria breaking down the sweat that causes the smell.
The ducts of apocrine sweat glands empty into hair follicles.
These glands begin functioning at puberty. (Function unknown, but may act as sexual sweat gland).
Other types of apocrine sweat glands
- Ceruminous glands of the external ear canals. Ceruminous glands secrete cerumen aka ear wax.
- Mammary glands
Sebaceous oil glands
Sebaceous oil glands are widely distributed (but not on the palms and soles).
Sebaceous oil glands develop from hair follicles and secrete into hair follicles.
These glands are stimulated by hormones (from puberty onward).
Sebaceous oil glands secrete sebum (they are holocrine glands: the gland breaks apart).
More about sebaceous oil glands:
- They have an oily holocrine secretion
- They have bactericidal properties
- They soften hair and skin
Photo: Cutaneous glands
What are the 6 functions of the skin?
Protection
Body temperature regulation
Cutaneous sensations
Metabolic functions
Blood reservoir
Excretion of wastes
3 Skin Barrier Protections
- The chemical barrier of the skin includes skin secretions (the acid mantle retards the multiplication of bacteria on the skin surface) and melanin.
- The physical barrier of the skin - the physical continuity of skin and the hardness of keratinized cells provides physical barriers.
The biological barrier of the skin - Both the dendritic cells of the epidermis and macrophages in the dermis can initiate immune responses.
Body Temperature Regulation
Unnoticeable sweat is called insensible perspiration.
Sensible perspiration: if body temp rises, dermal blood vessels dialate increasing sweat gland activities, producing noticeable sweat.
In cold external environments dermal blood vessels constrict, skin temp drops, resulting in slow passive heat loss.
Cutaneous Sensory Receptors
Cutaneous sensory receptors are part of the nervous system;
Exteroreceptors respond to stimuli outside the body, such as temperature and touch;
Free nerve endings sense painful stimuli.
Photo: skin structure
Metabolic functions of skin
- Skin synthesizes vitamin D for calcium production.
- Keratinocyte chemicals can disarm some carcinogens.
- Keratinocytes of the skin can activate some hormones (convert cortisone into hydrocortisone)
- Skin makes collagenase (aids in natural turnover of collagen to prevent wrinkles).
Skin as a blood reservoir
Skin can hold up to 5% of body’s total blood volume.
Skin vessels can constrict to shunt blood to other organs (i.e. exercise muscles).
Skin excretion
Skin can secrete limited amounts of nitrogenous wastes (ie ammonia, urea and uric acid).
Sweating can cause salt and water loss.
What is the cleavage line?
Cleavage lines are topological lines drawn on a map of the human body. They are parallel to the natural orientation of collagen fibers in the dermis, as well as the underlying muscle fibers.
Hair matrix
The hair matrix is the actively growing portion of the hair follicle consisting of a collection of epidermal cells that rapidly divide, move upward, and give rise to the hair shaft and the internal root sheath.
Hair papilla
Hair dermal papilla cells are specialized mesenchymal cells that exist in the dermal papilla located at the bottom of hair follicles. These cells play pivotal roles in hair formation, growth, and cycling.
