chapter 4+5
protects against abrasion, heat, chemicals, and microbes
keratin
inhibits water evaporation
lipids released by lamellar granules
keeps skin and hair from drying out and contains bactericidal chemicals
sebum
prevents growth of some microbes
acidic sweat
protects damaging effects
melanin
phagocytize bacteria and viruses
macrophages
deepest layer, single row cuboidal or columnar keratinocytes that contain scattered keratin intermediate filaments
i. Stem cells undergo cell division to produce new keratinocytes
ii. Melanocytes and tactile are scattered among keratinocytes
stratum basale
8-10 rows of many-sided keratinocytes with bundles of keratin intermediate filaments
i. Produce coarser bundles of keratin than strum basale
ii. Contains projections of melanocytes and dendritic cells
stratum spinosum
3-5 rows of flattened keratinocytes in which organelles are beginning to degenerate (apoptosis)
i. Cells contain keratohyalin and lamellar granules
stratum granulosum
converts keratin intermediate filaments to keratin
keratohyalin
release lipid-rich, water-repellant secretion
lamellar granules
present in fingertips, palms and soles
i. 4-6 rows of clear, flat, dead keratinocytes with large amounts of keratin
Lucidum
few to 50 or more rows of dead, flat keratinocytes that contain mostly keratin
Corneum
make up 85% of epidermal cells; produce keratin and lamellar granules
Keratinocytes
make up 8% of epidermal cells; produce melanin
Melanocytes
make up 5% of epidermal cells; arise from bone marrow, participates in immune responses, easily damaged by UV light, also known as intraepidermal macrophages
Dendritic cells (Langerhans cells)
make up 2% of epidermal cells; deepest layer, connect with sensory nerves cell (Merkel disc)
Tactile epithelial cells (Merkel cells)
patterns of loops and whorls and straight lines found on palms, soles, toes and fingers
Epidermal ridges
projections of the epidermis that project into the papillary dermis between the dermal papillae
Epidermal pegs
stretch marks
Striae
Found in certain areas of the body in the reticular dermis where collagen fibers line up more in one direction than another due to the natural tension of the skin due to bony projections, muscle orientation and joint movements
tension lines
increase friction and grip
formed by sweat gland secreations on top of the epidermal ridges
fingerprints
tough protective protein
i. Waterproofs skin
ii. Protects against abrasion and penetration
iii. Render body relatively insensitive to biological, chemical, and physical assaults
keratin
process of replacing viable cells in the stratum basal with more and more of the waxy keratin protein as cells move from the deepest layer to the surface layer that helps protect the skin
i. Dandruff: excess of keratinized cells
keratinization
Also called subcutaneous layer, attaches skin to underlying tissues and organs
b. Functions as storage area for fat and contains large blood vessels to supply the skin
hypodermis
formed by melanocytes in melanosome from amino tyrosine. Absorbs UV light and prevents DNA damage
melanin
yellow to red
Pheomelanin
brown to black
Eumelanin
yellow-orange pigment stored in the stratum corneum and adipose tissue; precursor to Vit A used for pigments needed for vision
Carotene
red, oxygen carrying pigment in red blood cells – more affect in light sinned people
Hemoglobin
where is melanin produced?
in organelle melanosome
what amino acid is melanin produced from
tyrosine
what are frekles and age spots
clusters of melanin
where does hair color come from
amount and type of melanin present in the keratinized cells of the hair
decrese of melanin in the hair
gray hair
lack of melanin replaced by air bubbles
albino/white hair
stratum Basale cells proliferate and invade the dermis and hypodermis
i. Least malignant, most common
ii. Slowly growing and do not often metastasize
iii. 30% whites get in lifetime
iv. 99% cured
basal cell carcinoma
arises from stratum spinosum
i. Scalp, ears, lower lip as scaly, red raised bump
ii. Grows rapidly and metastasizes if not removed
iii. Radiation therapy or surgically removed
squamous cell carcinoma
i. Most dangerous – highly metastatic, resistant to chemo
ii. Wide surgical excision and immunotherapy
iii. Poor survival if over 4mm thick
Malignant melanoma
condition that results from androgens inhibiting hair growth in genetically predisposed adults
male pattern baldness
thinning of the hair which may be due to aging, surgery, high stress, high fever, certain drugs, poor diet
alopecia
a. Tightly packed, dead, hard keratinized epidermal cells
i. Protects distal end of digits
ii. Provide support to fingers to increase touch perception and manipulation
iii. Allow grasping and manipulation of small objects and can be used to groom body in various ways
nails
visible portion of nail
nail plate
extends over end of digit
free edge
portion buried in fold of skin
nail root
crescent shaped white area at proximal end of nail plate
lunula of nail
secures nail to finger/toe tip
hyponychium
stratum corneum at proximal nail
eponychium (cuticle)
produce new nail cells
matrix
connected to hair follicles
i. Sebum, Puberty
ii. Prevents hair and skin from drying out, keep skin soft
sebaceous gland
most numerous
i. Perspiration, Soon after birth
ii. Regulation of body temp, waste removal, stimulated during emotional stress
eccrine sweat gland
located mainly in hairy skin areas
i. Perspiration, Puberty
ii. Stimulated during emotional stress and sexual excitement
apocrine sweat gland
modified sweat glands located in the ear canal
i. Cerumen, Soon after birth
ii. Impede entrance of foreign bodies and insects into external ear canal, waterproof canal, prevent microbes from entering cells
ceruminous gland
eccrine and apocrine sweat glands
Sudoriferous
only skin damaged, usually no need for treatment
i. Ex. sunburn
first degree burn
skin and upper regions of dermis are damaged.
i. Partial thickness burn
ii. Blisters
iii. Heals in few weeks
second degree burn
entire thickness of the skin is damaged
i. Full thickness burn
ii. Appears grey-white, cherry red, or black
iii. Nerve endings destroyed
iv. Need skin grafting, antibiotics
third degree burn
occurs when superficial wounds affect only the epidermis
epidermal wound healing
When cells encounter one another they stop migrating (healing complete when all cells come in contact w/ one another)
Contact inhibition
Blood clot forms, unites wound edges. cellular and vascular responses eliminate foreign material and prepare for repair
inflammatory wound healing
Clot becomes scab, epithelial cells migrate below the scab to bridge the wound. Damaged blood vessels begin to regrow.
i. Fibrosis: fibroblasts synthesizing scar tissue
Migratory wound healing
extensive growth of epithelial cells beneath scab, random patterns of dispositioned fibroblasts of collagen fibers. Continued growth of blood vessels
Proliferative wound healing
Epidermis restored to normal thickness, scab comes off, collagen fibers more organized and blood vessels restored to normal
Maturation wound healing
cell in deep wound healing
first cell in inflammation
Neutrophils
cell in deep wound healing
develop into macrophages as travel to wound
monocytes
cell in deep wound healing
develop into fibroblasts
mesenchyme
found where leak proof-seal is needed b/t cells to keep materials from leaking out of organs like the stomach and bladder
Tight junctions
attaches to microfilaments; keeps tissues from separating during contractile activities
Adherens
attaches to intermediate filaments; seen in skin to prevent cell separation during tension and in the heart to prevent cells from pulling apart during contraction
Desmosomes
attach to intermediate filaments of keratin; do not link cells to one another but to the basement membrane, attaching to the protein laminin
Hemidesmosomes
connexins form connexons that connect adjacent cells. Intercellular gaps allow passage of small molecules and ions but prevent passage of large molecules. Transfer nutrients in avascular tissues and allows communication between cells.
gap junctions
fluid-filled tunnels
connexons
how are cells of epithelial tissue arranged
in sheets and densely packed and attach to basement membrane
many cells junctions are present
what supports the epithelial tissue
connective tissue
avascular but does have a nerve supply
epithelial tissue
no blood vessels
avascular
has nerve supply
innervated
what occurs frequently in the epithelial tissue
mitosis
flat, wide “paving stone” cells
squamous
cells as tall as they are wide
cuboidal
cells taller than they are wide
columnar
one layer. All cells in contact with basement membrane - squamous, cuboidal, columnar
simple
appears to have layers, but all cells go from the apex to the base - columnar
Pseudostratified
Two or more layers. Only basal layer in contact with the basement membrane. – squamous, cuboidal, columnar
Stratified
specialized simple squamous epithelium that lies the entire circulatory system; reduces friction and turbulence of blood flow
Endothelium
specialized simple squamous epithelium found in serous membranes
Mesothelium
• Both derived from embryonic mesoderm (middle layer of the 3 primary germ layers of the embryo)
Endothelium & Mesothelium
• Unicellular exocrine gland; produces mucus.
• Found in respiratory and intestinal tracts.
goblet cell
secretory products are released into ducts that empty onto surface of a covering and lining epithelium, such as skin surface or lumen of hollow organ. Ex. Sweat, oil, earwax, saliva, digestive enzymes.
exocrine
secretions (hormones) enter intestinal fluid and then diffuse into bloodstream without flowing through a duct
endocrine
the most common manner of secretion
i. releases products by exocytosis and no part of gland are lost or damaged
Merocrine
“bud” their secretions off through the plasma membrane, producing membrane-bound vesicles in the lumen of the gland.
i. End of cell breaks of by “decapitation” leaving a milky, viscous odorless fluid
apocrine
produced by rupture of plasma membrane, releasing the entire cellular content into the lumen, and killing the cell
i. Cells are replaced by rapid division of stem cells.
holocrine
type of embryonic CT
give rise to all other connective tissues
Mesenchyme
type of embryonic CT
a gelatinous substance within the umbilical cord and is a rich source of stem cells
Mucous C.T. (Wharton’s Jelly)
1. Areolar
2. Adipose
3. Reticular
Loose CT
1. Regular
2. Irregular
3. Elastic
Dense
i. Hyaline
ii. Fibrocartilage
iii. Elastic
cartilage
i. Compact bone
ii. Spongy (cancellous) bone
Osseous (bone)
connective tissue
i. Loose
ii. Dense
iii. Cartilage
iv. Osseous (bone)
v. Blood