Ch. 5 Flashcards
What is the largest organ of the body?
Skin
What percentage of total body weight does the skin account for?
About 7%
What area does the skin cover?
2m²
What is the thickness range of the skin?
Varies from 1.5 to 4.0 mm
Where is the skin thickest?
In the palms and soles of feet
What are the two main layers of the skin?
Epidermis and Dermis
What is the composition of the epidermis?
Made of epithelial cells
What is the composition of the dermis?
Made of fibrous connective tissue
What is located below the dermis?
Hypodermis
Is the hypodermis part of the skin?
Not truly part of the skin
What is another name for the hypodermis?
Superficial fascia
What type of tissue primarily composes the hypodermis?
Mostly adipose tissue
What are the functions of the hypodermis?
Attaches skin to underlying muscles, stores fat, acts as a shock absorber and insulator
What type of epithelium is the epidermis made of?
Stratified squamous epithelium, 4 or 5 layers thick
What types of cells are found in the epidermis?
Keratinocytes, Melanocytes, Langerhans cells, Merkel cells
What are keratinocytes?
Most of the cells in the Epidermis. They produce the protein keratin which creates the toughness of the skin. Connected to each other by desmosomes. Cells are made in the deepest layer and then pushed toward the surface.
What do melanocytes do?
Synthesize melanin. Melanin is deposited into keratinocytes and accumulates on the superficial surface to protect the DNA from UV rays.
What are Langerhans cells?
Cells that are macrophages. They have processes that surround keratinocytes and form a mostly continuous network.
What are Merkel cells?
Sporadic cells located at the epidermal border (dermal). They are attached to a sensory receptor.
What is the Merkel disc?
A sensory receptor formed by the combination of a sensory receptor and a Merkel cell. It functions as a light touch receptor.
What are the layers of the epidermis?
Stratum basale (germativum), Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum.
What is thick skin?
Thick skin has 5 layers and occurs in areas of high wear, such as the soles of feet, palms, and fingertips.
What is thin skin?
Thin skin has 4 layers, with all layers being thinner, and it covers the rest of the body.
What characterizes the stratum basale (germativum)?
The stratum basale is a single cell layer thick, primarily composed of rapidly reproducing keratinocytes, with 10-25% of the cells being melanocytes and the presence of Merkel cells.
What is the structure of the stratum spinosum?
The stratum spinosum is several layers thick and contains a lot of pre-keratin. Cells begin to denature and crenate, giving them a spiny, prickly appearance.
What changes occur in the stratum granulosum?
The stratum granulosum is a thin layer 3-5 cells thick where cells flatten, nuclei and organelles begin to disintegrate, pre-keratin accumulates, and waterproofing glycolipid accumulates in the extracellular space. The cell membrane thickens.
What is the Stratum Lucidum?
Only found in thick skin and contains only a few layers of translucent cells. Pre-Keratin begins to change to keratin.
What is the Stratum Corneum?
The thickest layer of the epidermis, 20-30 cell layers thick. Pre-Keratin changes to keratin. Cells are flat and dead, appearing as shingles.
You lose about 40lbs of skin in a lifetime.
What are the components of the Stratum Corneum?
Keratin, thickened plasma membranes, and glycolipids between the cells.
What is the Dermis?
Made up of strong flexible connective tissue containing fibroblasts, macrophages, assorted other WBC’s, collagen, elastic fibers, reticular fibers, nerves, blood vessels, lymphatic vessels, hair follicles, oil glands, and sweat glands.
What are the two layers of the Dermis?
Papillary layer and Reticular layer.
What is the Papillary Layer?
A thin superficial layer made of areolar connective tissue with lots of blood vessels that supply the epidermis with oxygen and nutrients.
What are dermal papillae?
Projections into the epidermis that contain capillary loops, free nerve endings, and Meissner’s corpuscles.
What is the reticular layer?
About 80% of the dermal thickness, made of dense irregular connective tissue with thick bundles of collagen and elastic fibers.
What pigments cause the wide range of human skin color?
Melanin, carotene, and hemoglobin.
What is melanin?
A protein produced in melanocytes that ranges in color from yellow to reddish brown to black.
All humans have the same relative number of melanocytes; differences arise from the amount, color, and retention time of melanin.
What stimulates the production of melanin?
Damage to DNA by UV light.
What is carotene?
A pigment that is yellow to orange in color, accumulating in the stratum corneum and fatty tissue of the hypodermis.
Most obvious in the palms of hands where the stratum corneum is thickest.
What color is hemoglobin when oxygenated?
Crimson when oxygenated.
How does hemoglobin affect the appearance of skin in Caucasians?
Shows through the nearly transparent skin, making it appear pink.
What are the appendages of the skin?
Derivatives of the epidermis, including sweat glands, sebaceous glands, nails, and hair.
Where are sweat glands distributed in the body?
All over the body except nipples and external genitalia.
How many sweat glands are there per person?
Over 2.5 million per person.
What are the types of sweat glands?
Eccrine sweat glands, apocrine sweat glands, ceruminous glands, and mammary glands.
What are eccrine (merocrine) sweat glands?
The most numerous type of sweat glands, abundant on palms, soles, and forehead.
What is the structure of eccrine sweat glands?
Simple coiled tubular glands with ducts that open in a pore directly to the skin.
What is sweat composed of?
A hypotonic filtrate of blood, 99% water, with salts, antibodies, anti-microbial chemicals, and lactic acid.
What is the normal pH of sweat?
Normally pH of 4-6.
What controls sweating?
Sweating is controlled by the sympathetic nervous system.
Where does sweating start to prevent overheating?
Sweating starts on the forehead.
Where does sweating start when nervous?
Sweating starts on the hands, soles, and axillary region.
Where are apocrine sweat glands found?
Apocrine sweat glands are only found in axillary and anogenital areas.
Where do apocrine sweat glands’ ducts open?
Ducts open into hair follicles.
What do the products of apocrine sweat glands contain?
Products contain fatty substances and proteins.
More viscous; bacteria break down the product and create odor.
When do apocrine sweat glands begin to function?
They begin to function at puberty.
What may apocrine sweat glands be equivalent to?
They may be equivalent to sexual scent glands.
Where are ceruminous glands found?
Ceruminous glands are found in the external ear canal.
What do ceruminous glands secrete?
They secrete ear wax (cerumen).
What do mammary glands secrete?
Mammary glands secrete milk.
Are mammary glands found in both males and females?
Yes, they are found in both males and females.
When is mammary tissue fully developed?
Tissue is fully developed in women who are lactating or in the 3rd trimester.
What do sebaceous (oil) glands secrete?
Sebaceous glands secrete sebum.
Where are sebaceous glands not found?
They are not found in palms or soles.
How do sebaceous glands secrete sebum?
They secrete sebum into hair follicles or skin.
These are holocrine glands; sebum contains cell fragments and lipids.
What activates sebaceous glands?
Sebaceous glands are activated by puberty.
What is the function of sebum?
Sebum softens and lubricates the skin, prevents hair from becoming brittle, prevents water loss, and is bactericidal.
What are nails?
Nails are a scale-like modification of the epidermis made of hard keratin.
What are the structures of nails?
The structures of nails include the free edge (white tips), body (visible attached portion), and root (part embedded in the skin).
Where is hair found on the body?
Hair is found everywhere except the palms, soles, lips, nipples, and parts of external genitalia.
What are the functions of hair?
Hair senses insects, protects the scalp from sun, bumps, and heat loss, and eyelashes and nose hairs protect from insects and dust. Eyebrows protect eyes from sweat.
What is the structure of hair?
Hair is made of cells containing hard keratin and has a shaft and root with concentric layers: medulla, cortex, and cuticle.
What is a hair follicle?
A deep fold of epidermal tissue that ends in a swelling known as the hair bulb. The end of the hair is surrounded by a root hair plexus.
What is the Arrector Pili Muscle?
A bundle of smooth muscle associated with each hair follicle. Its contraction makes the hair stand up and creates goose bumps.
What causes goose bumps?
Goose bumps are caused by the contraction of the Arrector Pili Muscle due to cold or fear.
What are the functions of the integument system?
Protection, body temperature regulation, cutaneous sensation, metabolic functions, and excretion.
What are the types of protection provided by the integument system?
Chemical barrier, physical/mechanical barrier, and biological barriers.
What is a chemical barrier in the integument system?
Skin secretions that are acidic and kill many bacteria, producing human defensin which destroys bacteria cell walls.
How do skin wounds help prevent infection?
Skin wounds release chemicals to prevent Staphylococcus infections.
What is a physical/mechanical barrier?
A barrier that is waterproof and few things can penetrate it.
What substances can penetrate the physical/mechanical barrier?
Lipids soluble substances like vitamins, oxygen, carbon, and steroids; oleoresins like poison ivy and poison oak; organic solvents; heavy metals; and some drugs with the aid of penetration.
What are biological barriers?
Langerhan’s cells and white blood cells (WBCs) in the dermis.
How does the body regulate temperature?
By sweating to cool off, dilating blood vessels (flush) to cool off, and constricting dermal vessels to keep blood deeper when cold.
What are the types of cutaneous sensation?
Merkel discs for light touch, Pacinian receptors for hard touch, and bare nerve receptors for pain.
What is the metabolic function of the skin?
Sunlight begins the conversion of cholesterol to vitamin D, converts carcinogenic chemicals to harmless ones, converts harmless chemicals to carcinogenic ones, and activates steroid hormones.
What is excretion in the context of skin function?
Some loss of urea and ammonia, as well as salt loss.
Pancinian
hard touch
Merkel Disc
light touch
Bare nerve receptors
pain
What are the three types of skin cancer?
The three types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma.
What is basal cell carcinoma?
Basal cell carcinoma is the least serious and most common type of skin cancer.
It involves the proliferation of stratum basale cells that invade the dermis and hypodermis.
How does basal cell carcinoma grow?
Basal cell carcinoma grows slowly and does not often metastasize.
What is the cure rate for basal cell carcinoma?
Basal cell carcinoma can be cured by surgical excision in 99% of cases.
What is squamous cell carcinoma?
Squamous cell carcinoma arises from keratinocytes of the stratum spinosum.
Where does squamous cell carcinoma most often occur?
It most often occurs on the scalp, ears, and lower lip.
How does squamous cell carcinoma grow?
Squamous cell carcinoma grows rapidly and can metastasize if not removed.
What is the prognosis for squamous cell carcinoma if treated?
The prognosis is good if treated by radiation therapy or removed.
What is melanoma?
Melanoma is cancer of melanocytes and is the most dangerous type of skin cancer.
Why is melanoma considered highly dangerous?
Melanoma is highly metastatic and resistant to chemotherapy.
What are the characteristics of melanoma (ABCD)?
The characteristics of melanoma are:
A: Asymmetry; B: Border; C: Color; D: Diameter.
What does ‘A’ in the ABCD characteristics of melanoma stand for?
‘A’ stands for Asymmetry; the two sides of the pigmented area do not match.
What does ‘B’ in the ABCD characteristics of melanoma stand for?
‘B’ stands for Border; the border is irregular and exhibits indentations.
What does ‘C’ in the ABCD characteristics of melanoma stand for?
‘C’ stands for Color; the color can be black, red, brown, tan, or blue.
What does ‘D’ in the ABCD characteristics of melanoma stand for?
‘D’ stands for Diameter; the diameter is larger than 6 mm.
How is melanoma treated?
Melanoma is treated by wide surgical excision accompanied by immunotherapy.
What is the chance of survival for melanoma if the lesion is over 4mm thick?
The chance of survival is poor if the lesion is over 4mm thick.
