Chapter 5 Flashcards
What is the largest and heaviest organ of the body?
The skin
The skin can cover about 2 square meters and weigh 10-11 pounds.
What are the major functions of the skin?
- Protection
- Sensation
- Temperature regulation
- Vitamin D production
What are the two main layers of the skin?
- Epidermis- epithelial tissue
- Dermis - dense, irregular connective tissue
What is the primary fiber found in the dermis?
Collagen
What type of tissue is the epidermis composed of?
Stratified squamous epithelium, separated from dermis by a basement membrane.
Avascular - only bottom cells live
What are the main cell types found in the epidermis?
- Keratinocytes (produce keratin for strength) - most cells
- Melanocytes (contribute to skin color)
- Langerhans cells (immunity)
- Merkel’s cells (nerve cells to detect light and touch)
What are the five strata of the epidermis?
- Stratum basale - single layer of cells
- Stratum spinosum - limited cell division. Develop lamellar bodies
- Stratum granulosum - cells die here
- Stratum lucidum - thick skin only, soft keratin
- Stratum corneum - filled with lard keratin
What is psoriasis?
A chronic skin condition characterized by red, itchy scaly patches
What factors contribute to skin color?
- Pigments in the skin (major factor)
- Blood circulating through skin
- Thickness of stratum corneum
*Changes in blood flow (vasodilation, flushed skin, cold temp blue)
What is melanin?
A group of pigments responsible for skin, hair, and eye color
What role does melanin play in skin protection?
Absorbs UV rays and helps prevent damage to deeper tissues
What is the hypodermis also known as?
Subcutaneous tissue or superficial fascia
What is the function of the hypodermis?
Attaches the skin to underlying muscle and supplies it with blood and nerves
-contains 1/2 of body’s fat- functions at energy storage, insulation, padding
What is the difference between apocrine and merocrine sweat glands?
- Apocrine sweat glands: associated with hair follicles, active at puberty, viscous secretions
- Merocrine sweat glands: more numerous, widely distributed, mostly water secretions. Palms, soles,
What is the function of nails?
Protect ends of digits and aid in manipulation
Composed of hard keratin, grows continuously, modified stratum corneum layer.
What happens to skin as we age?
- Epidermis thins
- Collagen decreases, decreased elasticity
- Slower healing, infections more likely
- Decreased Vitamin D production by 75%
*melanocytes increase to age spots but decrease to cause pale skin
What is male pattern baldness?
When terminal hair of the scalp is replaced with vellus hair due to genetic factors and testosterone levels
What are stretch marks caused by?
Rupture of the dermis
What is the effect of chronic sun exposure on the skin?
Accelerates aging and causes changes in elastic and collagen fibers
What are the types of injections mentioned?
- Intradermal - goes into dermis. TB
- Subcutaneous- extends to subQ
- Intramuscular - through skin into muscle
How does Vitamin D affect calcium levels in the blood?
- Stimulates absorption from intestines
- Promotes release from bones
- Decreases loss from kidneys
Desquamation
Cells of the deeper layers of the elidermis undergo mitosis and move toward the surface, older cells slough off
Keratinization
As cells move outward through the layers, they will fill with keratin, die, and serve as a layer that resists abrasion and forms a permeability layer
Characteristics of thick skin
Has all 5 epithelial strata but no hair follicles
Found in areas subject to pressure or friction
Papillae of underlying dermis in parallel rows gives rise to fingerprints and toe prints
Characteristics of thin skin
More flexible than thick
Covers rest of body
Mostly contains hair follicles
Callus
Increase in number of layers in stratum corneum. A corn forms when this is over a bony prominence
What is melanin produced by
Melanocytes, which package melanin into vescicles (melanosomes)
Factors affecting melanin production
Genetics
Uv light
Hormones - MSH
Pregnancy
NOT due to number of melanocytes
Carotene
Yellow pigment found in plants such as carrots and corn. Can deposit in adipose and stratum corneum, tinting skin
Dermis
Responsible for the structural strength of the skin
Mostly CT- Contains nerve receptors, hair follicles, smooth muscle, blood vessels, glands, and lymph vessels, sensory receptors
Layers of the dermis
Papillary- superficial. Areolar CT. Has dermal papillae which form the fingerprints (friction ridges)
Reticular- Inner layer of dense CT. Collagen and elastic fibers arranged in lines of cleavage (tension lines)
How does fat distribution change
With age and endocrine conditions (puberty)
What is the hypodermic composed of
Adipose, but also stellar with collagen and elastic fibers
Classes of hair
Lanugo (fetal)
Vellus (short, no pigment)
Terminal (pigmented) - head, eyebrows
Intermediate (combo)- arms legs
How is hair color determined
Amount of melanin
Hair growth
Cyclic
With growth and rest phase
Growth rates
Eyelashes - grow 30, rest 105
Scalp- grow 2-5 years, rest 1-2 years
Functions of hair
Protection from UV
Blog entry (mucous in ears and nostrils)
Sensitivity to movement
Arrector pili muscles
Pull hsir follicle to elevate hairs
Glands
Sebaceous
Sweat
Apocrine
Merocrine
Ceruminous
Mammary
Sebaceous glands
Holocene glads that produce sebum. Most sebaceous glands have ducts to hair follicles
Prevents drying
Sweat glands
Apocrine
Merocrine
Ceruminous
Earwax. Combo of sebum and secretion
Mammary glands
Specialized spine glands that produce milk
What does sweat contain
Water, salt, urea, uric acid, and ammonia
What happens to
