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biology 1593 > Chapter 5 > Flashcards

Chapter 5 Flashcards

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1
Q

What are the layers of the skin

A
  • Epidermis
  • Dermis
  • Hypodermis
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2
Q

Structure of Epidermis

A
  • Superficial portion of skin
  • Composed of epithelial tissue (keratinized stratified squamous epithelium)

-Avascular, meaning it has no blood cells

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3
Q

Structure of Dermis

A
  • Deeper layer of skin
  • Composed primarily of connective tissue
  • Contains blood and lymph vessels, nerves, and other structures.
  • Made of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers produced by fibroblasts
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4
Q

Structure of Hypodermis

A
  • Also called the subcutaneous layer (sub Q)
  • Lies deep and below the dermis
  • Consists of areolar and adipose tissue which serves as an area for fat storage, blood vessel passage, and pressure nerve endings
  • Serves to connect skin to the underlying fibrous tissue of the bones and muscles
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5
Q

Name the layers of the epidermis

A
  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Startum corneum
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6
Q

Stratum basale

A
  • Deepest layer of the epidermis and contains some stem cells capable of undergoing cell division to form new cells.
  • Attaches the epidermis to the basal lamina (below the lamina is the dermis)
  • Cells in this layer bond to the dermis via the basement membrane; which is intertwining collagen fibers
  • Mostly a single layer of basal cells; which are cuboidal-shaped stem cells that help produce the keratinocytes of the epidermis.
  • Keratinocytes are produced in this layer which then produce new cells
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7
Q

Two other cells found among basal cells

A
  • Merkel cells; functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch. (Abundant on the surfaces of hands and feet)
  • Melanin: gives hair and skin its color and helps protect live cells of the epidermis from ultraviolet (UV) radiation
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8
Q

Dermal papilla

A
  • A finger-like projection or fold which is found superficially in the dermis.
  • Increases the strength of the connection between the epidermis and dermis.
  • The bigger the fold indications a stronger connection
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9
Q

Stratum spinosum

A
  • Provides strength and flexibility to the skin
  • Spiny appearance due to the protruding cell processes that join the cells via the desmosome
  • Desmosomes interlock with each other and strengthen the bond between the cells
  • Composed of 8-10 layers of keratinocytes and Langerhans cells; which functions as a macrophage by engulfing bacteria, foreign particles and damaged cells that occur in the layer.
  • Keratinocytes in this layer begin the synthesis of keratin and release a water-repelling glycolipid that helps prevent water loss from the body and makes the skin mostly water-proof
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10
Q

Stratum granulosum

A
  • Marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata
  • Also where a water-repellent sealant forms between the cells
  • Has grainy appearance from he changes of the keratinocytes being pushed into this layer
  • The cells in this layer become flatter, the cell membranes thicken, and they generate large amounts of the proteins keratin which is fibrous and keratohyalin.
  • Keratohyalin accumulates as lamellar granules within the cells. When cells die they leave behind cell membrane, keratohyalin and keratin which help form structure of skin and nails.
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11
Q

Stratum lucidum

A
  • Present only in the fingers, palms and soles
  • Smooth translucent layer
  • Keratinocytes in this layer are dead and flattened
  • Cells are densely packed with eleidin; which is a clear protein rich in lipids that are derived from keratohyalin which makes cells transparent and provides a barrier to water.
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12
Q

Stratum corneum

A
  • Most superficial layer; which consists of a lot of dead cells
  • Has lamellar granules that make it water-repellent
  • Constant exposure to friction causes this layer to increase in depth by forming a callus; which is an abnormal thickening of the epidermis
  • Has increased keratinization; or cornification that gives the layer its name. Cornification is keratinization plus the lamellar granules that form lipids that hold the dead keratinocytes together.
  • 15-30 dry dead layers that helps prevent the penetration of microbes and dehydration of underlying tissue.
  • Provides a mechanical protection against abrasion for more delicate underlying tissue.
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13
Q

Keratinization vs. Cornification

A
  • Keratinization is the process of keratinocytes in the basal cell layer maturing and dying to produce the stratum corneum layer.
  • Cornification is the increased keratinization plus the lamellar granules in the corneum that form lipids to hold the dead keratinocytes together.
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14
Q

Four cell types of the epidermis

A
  • Keratinocytes
  • Melanocytes
  • Langerhans cells
  • Merkel cells
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15
Q

Keratinocytes

A
  • Produce the protein keratin; helps protect the skin and underlying tissue from heat, microbes, and chemicals
  • Keratin produces lamellar granules, which produce water-repellent sealant
  • Keratinization; replacement of cells contents with the protein keratin, occurs when cells move to the skin surface within 2-4 weeks.
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16
Q

Melanocytes

A
  • Produces the pigment melanin; which contributes to skin color and protects skin by absorbing damaging UV light.
17
Q

Langerhans cell

A
  • Participates in immune response
  • Act as an outermost guard of the cutaneous immune system and are likely to induce the first reactions against pathogens encountered via the skin
18
Q

merkel cell

A
  • Touches a sensory structure called a tactile (merkel) disc and functions in the sensation of touch
19
Q

The two regions of the dermis

A
  • The dermis is composed of connective tissue containing collagen and elastic fibres and has two regions
  • The papillary layer
  • The reticular layer
20
Q

Papillary layer

A
  • Areolar connective tissue that contains fine elastic fibers, dermal papillae, corpuscles of touch (Meissner’s corpuscles), and free nerve endings for sensations of heal, cold, pain, tickle, and itch.
  • Superficial layer projects into the stratum Basale of the epidermis to form finger-like dermal papillae.
  • Sensory receptor in this layer is dermal papillae; indent the overlying dermis and house capillary loops and sensory receptors.
21
Q

Reticular layer

A
  • Under the papillary layer is the much thicker reticular layer.
  • Functions to strength skin and provide structure and elasticity.
  • It is composed of dense, irregular connective tissue that contains bundles of collagen fibers and some elastic fibers.
  • Sensory receptors in this layer is Pacinian corpuscles which detects pressure and vibration stimuli
22
Q

Epidermal ridges

A
  • Feature of the papillary layer of the dermis.
  • Caused by epidermis’s adaptation to the contours of the dermal papillae that are in the papillary layer of the underlying dermis.
  • Increases friction for better grasping ability and provides the basis for fingerprints and footprints.
23
Q

Pigments responsible for skin and hair color

A
  • Melanin (black, brown)
  • Carotene (yellow, orange)
  • Hemoglobin (in blood capillaries) -> lack of oxygen makes skin pale but with proper oxygen flow it returns back to normal pigment
24
Q

Melanin

A
  • Two types of melanin; eumelanin (black and brown) and pheomelanin (red)
  • Darker skin has more melanin produced by melanocytes than paler skin.
  • Helps prevent the breakdown of folic acid which is required process in the human body.
  • Too much melanin can interfere with vitamin D production which is needed to absorb calcium.
25
Q

Accumulation of melanin

A
  • The sun and UV rays stimulate keratinocytes to start manufacturing melanin by secreting chemicals that activate the melanocytes.
  • Melanocytes are the cells that synthesize melanin. They are found in the organelle melanosome. And the melanosome is found inside the keratinocyte.
  • A lot of melanin causes the skin to darken
26
Q

Cell that synthesizes and stores pigments

A
  • Melanocytes synthesize and store the pigment melanin
  • Epidermal cells synthesize and store the pigment carotene
  • Red blood cells synthesize and store the pigment hemoglobin in blood capillaries.
27
Q

General structure of hair

A
  • Hair consists of;
  1. Hair shaft; which is above the surface of the skin
  2. Root; that penetrates the dermis and subcutaneous layer
  3. Hair follicle; consisting of two epidermal layers surrounding the root
  • Non-living hair shaft and living hair root are continuous with each other and consist of an outer cuticle, inner medulla, and innermost cortex.
  • Hair follicle consists of;
  1. An enlarged base called the hair bulb
  2. A hair papilla that has many blood vessels to nourish the growing hair
  3. Hair matrix; that contains mitotically active cells to produce new hairs.
28
Q

Hair function

A
  • Provides protection
  • Thermal insulation
  • Sensing light touch
29
Q

Glands associated with the skin

A
  • Sebaceous (oil) glands
  • Sudoriferous (sweat) glands
  • Ceruminous glands
30
Q

Sebaceous (oil) glands

A
  • Usually connected to hair follicles; they are absent in the palms and soles.
  • They produce sebum, which moistens hairs, waterproofs and softens the skin and inhibits bacterial growth.
31
Q

Sudoriferous (sweat) glands

A
  • Divided into apocrine and eccrine types;
  1. Eccrine sweat glands; help to regulate body temperature through evaporation, and eliminate wastes such as urea.
  2. Apocrine sweat glands are limited to the skin of the axilla, pubis, and areolae; their ducts open into hair follicles.
32
Q

Ceruminous glands

A
  • Modified sudoriferous glands that produce a waxy substance called cerumen.
  • These glands are found in the external auditory meatus.
33
Q

Functions of the skin

A
  • Thermoregulation
  • Protection through physical, chemical, and biological barriers
  • Cutaneous sensations; touch, pressure, vibration, tickle, heat, cold and pain.
  • Excretion and absorption
  • Synthesis of vitamin D
34
Q

Protection of skin through physical, chemical, and biological barriers

A
  • Function of skin
  • Acts as a protective barrier against water loss
  • First line of defense against abrasive activity
35
Q

Sensory function (cutaneous sensations)

A
  • Function of skin
  • Skin acts as sense organ because the layers of the skin contain specialized sensory nerve structures that detect touch, surface temperature and pain.
  • Receptors are more accumulated on the tips of fingers, this includes the;
  1. Meissner corpuscle (tactile corpuscle) that responds to light touch
  2. Pacinian corpuscle (lamellated corpuscle) that responds to vibration.
36
Q

Thermoregulation

A
  • Function of skin
  • Through association with the sympathetic nervous system it helps regulate temperature.
  • Sweat glands release sweat to cool skin down.
37
Q

Vitamin D synthesis

A
  • Function of skin
  • Epidermal layer of human skin synthesizes vitamin D when exposed to UV radiation.
  • Vitamin D is essential for normal absorption of calcium and phosphorous which is required for healthy bones.
38
Q
A

biology 1593 (4 decks)

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