Chapter 5 Flashcards
What are the layers of the epidermis in thin and thick skin
Thin skin:
- stratum basale
- stratum spinosum
- stratum granulosum
- stratum corneum
Thick skin:
- stratum basale
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
What are the 4 cells of the epidermis
- keratinocytes
- melanocytes
- intradermal macrophage
- tactile epithelial cells
Describe the function of keratinocytes
- produce the protein KERATIN (which is tough and fibrous)
- protects skin and tissues below from abrasions, heat, microbes and chemicals
- produce lamellar granules which release a water repelling sealant that reduces water entry and loss, and can prevent entry of foreign materials through the skin
Describe the function of melanocytes
- develop from ectoderm of developing embryo
- produce the pigment MELANIN, which are long slender projections that extend between the keratinocytes and transfer melanin granules to them
- melanin granules form a veil over the nucleus the shield keratinocytes from UV light
What is the function of intradermal macrophages
- arise from red bone marrow and migrate to the epidermis
- immune response against microbes by recognizing them and destroying them
What is the function of tactile epithelial cells
- found in the the deepest layer
- contact the flattened process of a sensory neuron (nerve cell) called tactile disc/merkel disc
- they detect touch sensations
Structure of the stratum basale
- deepest layer of the epidermis
- composed of single row cuboidal and columnar keratinocytes that contain scattered keratin intermediate filaments (tonofilaments)
- some cells in this layer (stem cells) undergo cell division to produce the keratinocytes
- the nucleus is large, and cytoplasms has ribosomes, small Golgi complex, few mitochondria, and some rough ER
- melanocytes and tactile cells are scattered among the keratinocytes
Structure of stratum spinosum
- second deepest layer of the epidermis
- has numerous keratinocytes in 8-10 layers
- cells are superficial and flat
- contagions keratinocytes produced from the stem cells of the basale layer, and the same organelles with some ability to divide
- keratinocytes produce coarser bundles of keratin in intermediate filaments than the other layers
- cells are round and large but can shrink and pull apart, except where membranes join with desmosomes
- spine like projections insert into desmosomes, which join cells to one another
- provide strength and flexibility
- contain interdermal macrophages and projections of melanocytes
Structure of stratum granulosum
- the middle layer of the epidermis
- 3-5 layers of keratinocytes that undergo apoptosis
- nuclei and organelles begin to degenerate as they are further away from the nutrition source (dermal blood vessels)
- keratin intermediate filaments no longer get produced and organelles in the cells regress
- dark stained granules of protein (keratohyalin) assembling keratin intermediate filaments into keratin
- also present in keratinocytes are membrane-enclosed lamellar granules that fuse with the plasma membrane and release lipid-rich secretions (water repelling sealant that decrease loss and entry of water and foreign materials) that get deposited in spaces between cells of this layer and the deeper layers
Structure of stratum corneum for thick and thin skin
- thin skin has a few- 30 layers of flat dead keratinocytes that range in thickness while thick skin has 50+ layers
- cells are flat and thin with the plasma membrane enclosed packages of keratin (no nucleus or organelles)
- is the final product of cell differentiation
- layers overlap, neighbouring layers of cells form strong connections with others
- the plasma membrane of adjacent cells are arranged like puzzle pieces that fit together
- cells shed and get replaced from the deeper layers which help protect the deep layers from injury and microbe invasions
- constant exposure and friction stimulates increase cell and keratin production
Structure of stratum lucidum
- 4-6 layers of flat, clear, dead keratinocytes with large amounts of keratin and a thick plasma membrane
- found at thicker skin regions like fingertips, palms and soles
What is apoptosis
Orderly, genetic program of cellular death, where the nucleus fragments before cells die off
Rate of cell division in stratum basale _________ when the outer layers of the epidermis are injured
Increases
What is the epidermal growth factor
A hormone like protein that speeds up cell division when other layers are damaged and regulates the growth
What is keratinization
New formed cells are pushed to the surface from one epidermal layer to another, and accumulating more keratin as it goes
Apoptosis occurs and cells slough off and get replaced
Structure of the dermis
- deep to the epidermis
- composed of dense irregular connective tissue
- contains collagen and elastic fibres (allowing for tensile strength- can stretch and recoil)
- thicker than the epidermis
- cells are fibroblasts, some macrophages, and few adipocytes
- contains blood vessels, nerves, glands and other embedded hair follicles
- essential for epidermis survival
- has 2 layers (thin superficial papillary and thick deep reticular)
What are the differences between the 2 dermal layers
— thin superficial papillary
(1/5th of thickness of dermis)
(contains THIN collagen and FINE elastic fibres, and an AREOLAR connective tissue)
(Dermal ridges that house blood capillaries, corpuscles of touch me free nerve endings)
— thick deep reticular
(4/5th of thickness of the dermis)
(Contain THICK collagen, COARSE elastic fibres, and DENSE IRREGULAR connective tissue)
(Has spaces between the fibres that contain adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands)
What is the basis for different skin colors
- melanin, hemoglobin, and carotene (all are pigments)
- melanocytes are the same in all people, however the amount of pigment that the melanocytes produce and transfer to keratinocytes is what makes the difference in skin color
Structure of hair (pili)
Composed of dead keratinized epidermal cells bonded by extracellular proteins
- hair shaft
- hair root
- hair follicle
- hair bulb
Hair shaft
Superficial part of hair, above skin surface
Hair root
Deep to the shaft, penetrates the dermis and subcutaneous layer
Has 3 layers:
- inner medulla: irregular cells; large amount of pigment
- middle cortex: form large part of shaft, elongated cells
- cuticle: outermost layer, thin flat cells, heavy in keratin
Hair follicle
-external root sheath; downward continuation of epidermis
- internal root sheath: forms cellular tubular sheath of epithelium between external sheath and hair
Hair bulb
At the base of the follicle
Houses papilla of hair, contains areolar connective tissue and blood vessels to nourish hair
Contains hair matrix from stratum basal where cell division occurs to produce new hair
Hair has _________ glands and bundles of ___________ muscle cells
Sebaceous and smooth
(Smooth muscle cells are called arector pili) - extends from the superficial dermis of skin to the dermal root sheath surrounding the hair follicle
Where is the distribution of hair
What determines the thickness of growth
Most of the skin other than thick skin locations like palms and soles
Genetics, hormones
Functions of hair
- protection (of scalp from sun and injury- like lashes and brows from foreign materials entering the eyes)
- touch receptors (hair root plexus)
- physiological and emotional stress causes autonomic nerve endings to stimulate the arector pili (smooth muscle cells) to contract, and pull the hair shaft so it sticks up (goose bumps)
Three types of skin glands
Sebaceous, sudoriferous, ceruminous
What is the Sebaceous gland secretion, structure, distribution and function
Secretion: oil
Structure: branches of acinar glands connected to hair follicles
Distribution: dermis anywhere that hair is located, open directly to the skin surface of lips, reproductive region, tarsal glands of eyelids
Function: secrete oily substance (such as sebum) that coats the skin surface to keep it from drying out, and keep hair from becoming brittle, prevents excessive evaporation of water, and keeps skin soft, prevents bacterial growth
What is contained in sebum
Triglycerides, cholesterol, protein, inorganic salts
What is the sudoriferous secretion, structure, distribution, and function
Secretion: sweat
Structure: eccrine glands are simple, coiled and tubular and small ducts, appocrine glands are simple, coiled, and tubular with large ducts and lumens
Distribution: eccrine sweat glands are throughout the skin other than lips, reproductive regions and ears, with the secretory portion in the deep dermis with a pore at the epidermal surface. Appocrine is found at the skin of the axilla, groin, areola and beard region of males
Function: release of sweat to perspirate through pores, eliminate wastes, regulate body temp, and creates body odour when interacting with bacteria
What wastes do sudoriferous glands excrete
Water, small ion, urea, uric acids, amino acids, lactic acids; ammonia
What is the difference in sensible and insensible thermotegulatory sweating
- occurs 1st on the forehead and scalp, then extends to the rest of the body. Sweat evaporates from the skin before it is perceived as moisture (insensible perspiration)
-When sweat gets excreted in large amounts where moisture is seen, it is called sensible perspiration
Where does sweating occur when going through emotional stress
First occurs on the Palms and soles and axillae before spreading to the rest of the body
What is the ceruminous glands secretion, structure, distribution, and function
Secretion: wax
Structure: coiled tubular glands with ducts and rounded clusters of dilated tubules
Distribution: external ear canal
Function: produce the waxy substance that is lubricating (called cerumen), the cerumen is secreted in the subcutaneous layer deep to the sebaceous glands where the excretory ducts open directly to the surface of the auditory canal OR into the sebaceous gland ducts. Cerumen works with ear hairs to provide a sticky barrier to prevent entry of foreign bodies. It is waterproof to prevent bacteria and fungi from entering
What is the 7 structures that make up the nail
Nail body/plate
Free ridge
Hyponychium
Nail root
Mail bed
Eponychium
Nail matrix
What makes up the structure of the nail plate
Flat keratinized cells and blood capillaries
Structure of the free ridge of a mail
Extends past the distal end of the digit has no capillary but has keratin cells
Structure of the hyponychium
Beneath the free ridge, and between the free ridge and skin
Contained in the nail root
Lanula: the white moon shape proximal of the nail, has vascular tissue, thickened epithelium
Nail bed lacks:
The epidermis of the nail lacks a stratum granulosum
The eponychium is also known as the
Cuticule
The cuticle consists of:
Stratum corneum
It’s a narrow band that extends and adhered to the lateral border/nail wall
The nails matrix has no:
Nuclei, only matured keratinocytes
Distribution of the nail body
The visible portion above the epithelium and dermis
Distribution of the nail root
Buried under the skin fold
Distribution if the lanula of the nail
Proximal end that is visible to the eye above the the epithelium
Distribution if the nail bed
Distal to the lanula, below the nail plate extends to the hyponychium (the pink of the nail)
Distribution of the eponychium
Proximal border of the nail, the raised part
Distribution if the nail matrix
Proximal to the nail root
Function of the hyponychium
Secured the nail to the fingertip
Function of the nail matrix
Where cells divide mitotically to produce new nail cells
Overall function of nails
Protect finger tips, provide support and counter pressure to the palmar surface
Enhances touch and perception
Allow grasping and manipulation
How does skin act as a blood reservoir
The dermis houses a network of blood vessels that take up about 8-10% of total blood flow in the body
How does skin work for body regulation
Liberates sweat at the surface in response to high environmental temperatures by heat production (exercises)
The sweat produced from the eccrine glands increase sweat evaporation and decrease body temp
When there is low temperatures, the body reduces sweat production to conserve heat
Another way, is the flow of blood in the dermis (vessels dilate, increasing the flow) therefore increasing the heat loss from the body
In low temperatures; the vessels constrict, decreasing blood flow, decreasing heat loss and the skeletal muscles contract to generate heat (shivering)
How does skin work for protection (6 ways)
-keratin protects tissues from microbes, heat and chemicals by tight interlocking keratinocytes that resist invasion
-Lipids released by lamellar granules prevent evaporation of water from the skin and protect from dehydration or allowing water to enter
- sebum keeps skin and hair from drying out and contains a bactericides chemical
- acid pH of perspiration decrease microbe growth
- melanin shields from UV light damage
- immunity by intraepidermal macrophages (recognize and process microbes and phagocytosis)
How does skin work for sensation
Senses touch, pressure, vibrations, tickling, thermal; and pain by having a wide variety of nerve endings and receptors (tactile discs of epidermis and corpuscles of touch in the dermis; and hair root plexuses of hair follicles)
How does skin work with excretion
Eliminates substances through sweat, the stratum corneum cells are waterproof, they evaporate sweat
How does skin work with absorption, what kind of products get absorbed
Passage of materials from the external environment to the inside of body cells. Lipid soluble materials like vitamins; drugs, gases, organic solvents, and topical steroids
How does vitamin D work in the skin
Activated by precursor molecules in the skin by UV light
- enzymes of the liver and kidneys modify the activated molecules, and produce calcitrol (hormone that aids in absorption of calcium from food into the blood via GI tract)
- activated vitamin D respond to infection by enhancing phagocytotic activity, which increases production of anti microbial substances in phagocytes to regulate immune function and decrease inflammation
