2 - Integumentary System

that type of tissue is the epidermis made of?

epithelial tissue

what type of cell is epidermis made of?

stratified squamous epithelium

in what layer of skin do we deposit fat?

hypodermis

describe the hypodermis.

underlying subcutaneous layer of adipose and areolar connective tissue

true or false: the hypodermis is considered part of the integumentary system.

false

in order of exterior to interior, name the main “skin” layers.

epidermis, dermis, hypodermis

what are the layers of the dermis?

papillary layer and reticular layer

what composes the cutaneous membrane?

epidermis and dermis

how does the integumentary system regulate body temperature?

it regulates

• conductive/convective heat loss

• evaporative heat loss

describe conductive heat loss.

heat transfer from different states of matter

describe convective heat loss.

heat transfer from solid to solid

• ex: hand on window, hand becomes cold

what is the role of blood vessels in heat loss/preservation?

they constrict/dilate to regulate blood flow to skin

• constrict → keep heat

• dilate → transfer heat from blood to environment

what regulates skin blood flow?

neural mechanisms

what controls evaporative heat loss?

neural regulation

when the body gets too cold, what sends signals to the control center?

thermoreceptors

what is the control center of homeostasis?

hypothalamus

what is the function of Vitamin D?

it signals to intestines to increase absorption of calcium and phosphorus

describe rickets.

weak/bendy structurally abnormal bone due to lack of calcium and phosphorus

what is the inactive form of Vitamin D?

cholecalciferal

what is the thickness range of the epidermis in thin skin?

0.10-0.15 mm

what is the thickness range of the epidermis in thick skin?

0.5 - 4.5 mm

what separates the epidermis from the underlying dermis?

basement membrane

describe blood flow throughout the epidermis.

avascular

what is the function of epidermal ridges?

project into dermis to increase SA → creates more pts of attachment

where on the body is thick skin found?

palms and soles of feet

how does cell shape change as cells move from basement membrane to outer epidermis

cuboidal → flat, squamous

what are the different cell types of the epidermis?

• keratinocytes

• stem/basal cells

• melanocytes

• merkel cells

• Langerhans/dendritic cells

what is the most abundant cell type of the epidermis?

keratinocytes

what is the function of lamellar granules?

lipid secretions

• lipids → hydrophobic

• its secretions form a barrier that keeps water in and out of the body

• “waterproofs” skin

in order of most to least, where is keratin found in the body?

nails → hair → skin

where are stem cells found in the epidermis?

stratum basale (deepest layer)

what is the function of stem cells?

go thru mitosis (unipotent)

• give rise to keratinocytes (mitosis → 1 stem cell, 1 keratinocyte)

where are melanocytes found in the epidermis?

stratum basale

what is the function of melanocytes?

to produce melanin (pigment)

where are Merkel cells found in the epidermis?

stratum basale

what is the function of Merkel cells?

mechanoreceptors

• detect (thanks to sensory neurons) light touch

what are the components of Merkel’s disc?

a tactile cell in epidermis and its nerve ending

where are Langerhans/dendritic cells found in the epidermis?

stratum spinosum

how do Langerhans cells move?

using actin

what is the function of Langerhans cells?

immune response against microbes and cancers

• phagocytosis

how long does it take to create the layers of the epidermis up to the corneum?

one week

how long does it take to create the layers of the epidermis in thick skin?

three weeks

what is the function of a melanosome granule?

prevent UV light from getting into nucleus and destroying DNA

how are melanosome granules destroyed?

degraded by lysosomes in keratinocytes

what stimulates the production of melanin?

exposure to UV light

what two factors affect skin color?

epidermal pigmentation and blood flow to the skin

what is the yellow-red component of melanin called?

pheomelanin

what is the brown-black component of melanin called?

eumelanin

what is the relationship between melanin and VD production?

inverse

• the more melanin in skin, the less VD the body produces from exposure

• melanin is an inhibitor of VD absorption

what color is oxygenated blood?

bright red

what color is deoxygenated blood?

dark red/purple

describe erythema

localized area of redness

• due to excess blood in dilated vessels

what are the different layers of the dermis?

papillary and reticular layer

define papilla.

n*pple-shaped

describe the papillary layer of the dermis.

topmost layer

• has dermal papillae

• vascular areolar tissue

describe the reticular layer of the dermis

deeper layer

• dense connective tissue with abundant collagen and elastin fibers

what structures are in the dermis?

• blood vessels

• lymphatic vessels

• nerves and sensory receptors

• hair follicles

• glands

what is the function of lymphatic vessels?

to help recycle ECF and drain excess fluid

what are the three types of sensory receptors in the IS?

mechanoreceptors, nociceptors, and thermoreceptors

what are the mechanoreceptors of the integumentary system?

• merkel’s discs

• Meissner’s corpuscle

• Ruffini ending

• Pacinian (lamellated) corpuscle

• nerve endings

what is the function of the Merkel’s discs?

region where cell talks to neuron

• touch and pressure - mechanical disruption

• equally distributed throughout body

where are Meissner’s corpuscles found?

in dermal papillae of glabrous skin

• skin with no hair

• ex: lips, palms, soles, genitalia

describe the function of Meissner’s corpuscle.

sensitive to fine touch and pressure

where is the Ruffini ending located?

in the deep dermis

what is the function of the Ruffini ending?

sensitive to skin distortion and pressure

where are lamellated corpuscles located?

in the deep dermis/hypodermis

what is the function of the Pacinian corpuscle?

sensitive to deep pressure and vibration

what mechanoreceptor detects hair movement?

the neuron/nerve ending surrounding each hair root

what is the structure and function of nociceptors?

• sensitive to painful stimuli

• free nerve ending

what is the structure and function of thermoreceptors?

• sensitive to temperature

• free nerve endings

what is the composition of nails?

dense layers of dead, heavily keratinized, keratinocytes

what is the function of nails?

• protection

• limit distoriton

• tools

• help distribute tension

describe the nail root.

deep epithelial fold

• contains stratum basale that gives rise to the nail

describe the nail body.

visible portion of the nail

describe the nail bed.

the epidermal layer just below the nail body

describe the lunula.

the base of the nail where blood vessels are not visible

• living part of nail matrix

• white bc cannot see blood vessels

describe the eponychium.

the cuticle

• an extension of stratum corneum from the root over base of nail

why is the tip of the nail white?

because the cells are no longer metabolically active

describe the composition of hair.

dead, keratinized cells which project above the surface of the skin

where is hair produced?

hair follicles

• organs within the dermis

what are the two types of hair on skin?

vellus hair of terminal hair

describe vellus hair.

small, short, and delicate

• no melanocytes

describe terminal hair.

large, course, pigmented

• melanocytes in hair follicle deposit pigment/melanin into hair)

what is a follicle?

specialized invagination of epidermis withing surrounding connective tissue sheath

describe the two structures in the base of the follicle.

hair papilla: indentation in connective tissue (blood vessels)

hair bulb: surrounds papilla; site of production of growing cells

describe the hair root.

anchors hair

• from base to halfway to skin surface

• contains living cells

describe the hair shaft.

dead cells

• extends from halfway point to surface

how much does hair on the scalp grow?

0.33 mm per day

describe the hair matrix.

within hair bulb

• site of epidermal stem cells

  • divide, one is pushed up and keratinized

from inner to outer layers of hair, there is ____ to ____ keratin.

less, more

what are the layers, in order of inner to outer, of hair?

medulla, cortex, cuticle

where is keratinization of hair complete?

at border of root and shaft

what are the layers, in order of inner to outer, of epithelial cells that line the follicle?

internal root sheath → external root sheath → glassy membrane

what are the three secretion modes?

merocrine, apocrine, and holocrine

describe merocrine secretion.

secretory vesicles are discharged at the apical surface of the gland cell by exocytosis

what gland in the body uses merocrine secretion?

salivary glands

describe apocrine secretion.

1. secretory products gather at apical end of cell

2. apical cap pinches off and breaks down to release stuff

3. cell survives, repairs apical tip

what gland in the body uses apocrine secretion?

mammary glands

describe holocrine secretion.

1. cell division replaces lost cells

2. cells produce secretion → increase size + move up stratified layers

3. cells burst to release stuff (does not survive)

what type of gland in the body uses holocrine secretion?

sebaceous gland