14 - The Integumentary System

order of the layers of the integument

epidermis, basement membrane, dermis, subcutaneous

epidermis epithelium

stratified squamous keratinized epithelium

avascular

keratinocytes function and development

produces keratin and waterproof

initially cuboid or columnar then turns squamous, fills with keratin and loses nucleus and organelles

keratin structure

cytoskeleton made of intermediate filaments

hemidesmosomes anchor to basal lamina
desmosomes have cell-cell adhesions

keratinocyte layers

stratum corneum

stratum lucidum (only in thick skin)

stratum granulosum

stratum spinosum

stratum basale

stratum basale

a single layer of replicating keratinocytes that renews epidermis every 15-30 days

hemidesmosome attachments to basement membrane

accept melanin granules from melanocytes

stratum spinosum

thickest in thick skin

polyhedral shape, central nucleus

active keratin synthesis

spines and desmosomes

stratum granulosum

3-5 layers of rhomboidal cells

completion of keratinization process - decreased organelles in cell, increased keratin

formation of barrier against water loss

contents of cells of stratum granulosum

tonofibrils

keratohyalin granules - forms tight barriers that protect against foreign particles

lamellar granules/bodies exocytose lipids and glycolipids that help with waterproof

stratum lucidum

only in thick skin

cells are translucent

keratinocytes are flat, with no nucleus or organelles, have desmosomes

packed with keratin

stratum corneum

15-20 layers of fully keratinized cells, are squamous shaped with no nucleus or organelles

desquamation - shedding of skin

other cells in the epidermis include:

melanocytes

Langerhan’s cells

Merkel cells

where are melanocytes located and what do they do?

located in the stratum basale

produce eumelanins (black and brown pigments)

what are melanosomes?

vesicles of eumelanins (pigments) that are released from melanocytes and taken up in keratinocytes

what are eumelanins and what do they do?

black and brown pigments that collected above nucleus in keratinocytes

protect DNA by scattering UV light and are degraded over time

Langerhans Cells function, derivation and location

antigen presenting immune system cells that trigger immune response against microorganisms in epidermis

derived from monocytes

located in the cell body in spinosum layer

Merkel cells function, location

tactile cells for light touch, unmyelinated afferent nerve fibers

found in basal layer (basement membrane) of epidermis, numerous in fingertips and hair follicles

carcinomas of epidermis include:

keratinocyte origin - basal cell carcinoma and squamous cell carcinoma (originate spinous layer)

malignant melanoma

Merkel cell carcinoma

dermal-epidermal junction (basement membrane) is composed of…

has epidermal papillae

made of Type IV collagen

PGs and laminin

hemidesmosomes - anchor to type VII collagen

nutrients for epidermis diffuses through the basement membrane

layers of the dermis

papillary (superficial) and reticular (deep)

papillary dermis type of CT, cells, vascular?

LCT

has fibroblasts, macrophages, dendritic cells, mast cells, leukocytes

has capillaries, lymph, nerves

ECM of papillary dermis

fibers include collagen, elastic, and reticular that are disorganized

ground substance contains small PG, GP, proteins

reticular dermis type of CT, cells, vascular

DICT

less cells than LCT, same types as papillary but mostly fibroblasts

blood vessels are near surface and help with thermoregulation

dermal blood vessels function?

support/nourish epidermal and dermal cells

role in regulation of temperature and BP, arteriovenous shunts help with this

subcutaneous (hypodermis) tissue type

LCT with many fat cells, between integument and organs

what are the types of somatic afferent innervation?

nociception

thermal

mechanical/tactile

what structures have sympathetic innervation?

vessels (adrenergic —> vasoconstriction, cholinergic —> vasodilation)

glands

arrector pili muscles

what structures have parasympathetic innervation?

vessels of the skin of the face only

pacinian corpuscle location and function

reticular dermis and subcutaneous layer

responsible for sensing coarse touch, pressure and vibration

Meissner corpuscle location and function

dermal papillae, perpendicular to surface, fingertips, palms, soles of feet

sensory functions include light touch, low frequency

where is the hair bulb located?

indented by dermal papilla - stratum basale progenitor cells

arrector pili muscle

smooth muscle

sebaceous gland function

produce sebum into hair follicle through holocrine secretion (breaking down entire cell/rupture)

nail matrix consists of

proliferative keratinocytes, become keratinized as pushed to nail root

where are sebaceous glands located?

in dermis

epithelial cells- outer mitotic

acne vulgaris

build up of secretions under skin due to increased sebum and blocked hair follicle

eccrine sweat glands location

everywhere

types of cells in eccrine sweat glands

clear cells - transport ions and fluid into duct

dark cells - glycoprotein secretions

eccrine sweat gland function and characteristics

in dermis and extends to basal layer of epidermis

thermal regulation and excretion of nitrogenous wastes and electrolytes

is controlled sympathetically (cholinergic)

glandular portion: has clear and dark cells

surrounded by rich capillary network and myoepithelial cells

ducts reabsorb Na+

is a merocrine secretion

apocrine sweat gland location

in the axillary and perineal regions

apocrine sweat glands function and characteristics

secretory portion is in the dermis and hypodermis

glandular portion secretions are viscous and odiferous via merocrine secretion

pheromones

controlled by sympathetic nervous system (adrenergic) - ex: emotional stress

ducts usually lead to hair follicles