C5

Question 1

INTEGUMENTUM:

Answer 1

skin and appendages: largest organ; forms 7% of body weight.

Question 2

Components:

Answer 2

epidermis=keratinized stratified squamous epithelium + dermis=CTP: papillary and
reticular layer.

Hypodermis=subcutaneous tissue=superficial fascia: adipose tissue deep to dermis; not considered skin)

Question 3

TYPES:

Thick skin:
Thin skin:

Answer 3

Thick skin: epidermis has five strata; present on the soles of feet and palms of hands; no hair
or sebaceous glands.

Thin skin: epidermis has four strata; contains hair and sebaceous glands; present everywhere else

Question 4

FUNCTIONS

Answer 4

1. Protection: against impact, dehydration, pathogens, UV radiation.
2. Body temperature regulation: vasoconstriction: decrease of blood vessel diameter
   shunts blood away from surface to maintain heat; vasodilation: increase of blood
   vessel diameter brings blood to skin to dissipate heat; sweat.
3. Excretion: of urea, water, salts released via sweat.
4. Production of vitamin D: epidermal cells utilize UV radiation to produce vitamin D, which
   facilitates absorption of calcium from GI tract.
5. Sensory reception. Epidermal: Merkel=Tactile cells for light touch. Dermis: receptors for
   pain, pressure, heat, stretch. Hair: root hair plexuses as touch receptors.

Question 5

EPIDERMAL STRATA
from basal to apical border:

Answer 5

1. Stratum basale=stratum germinativum: site of most mitosis; consists of a single row of cells that
   rests on basement membrane; cells: keratinocytes, Merkel=tactile cells (touch receptors);
   melanocytes (synthesize and transfer melanin pigment to keratinocytes).
2. Stratum spinosum: several rows of cells: keratinocytes exhibit “spider-like” artifact processes
   created at desmosomes; dendritic=Langerhans cells serve to initiate immune response to
   foreign antigens.
3. Stratum granulosum: several rows of flattened keratinocytes containing keratohyaline granules
   (precursors to keratin).
4. Stratum lucidum: present in thick skin only; consists of several rows of dead keratinocytes.
5. Stratum corneum: many rows of dead keratinocytes at apical border; thicker in thick skin

Question 6

DERMIS

Answer 6

1. Papillary layer: superficial 20%; loose=areolar CTP; thicker in thick skin; forms “finger
   “prints” (sweat pores that open onto skin surface).
2. Reticular layer: 80%, dense irregular CTP; collagen bundles prominent; primary orientation of
   collagen determines tension=cleavage lines determine incision lines followed in surgery.
   Flexure lines: visible skin creases resulting from repeated folding of skin.
   Blood supply: dermal plexus located between dermis and hypodermic; subpapillary layer located
   between papillary and reticular layers.

Question 7

GLANDS

Answer 7

1. Sebaceous=oil; simple alveolar; secrete sebum via holocrine method onto hair follicles;
   sebum: protects, moisturizes, decreases water loss across skin, helps kill bacteria.
2. Sweat=sudoriferous: true sweat: water, salts, urea; excretes, cools, slows bacterial growth.
   a. Eccrine: simple coiled tubular; duct opens onto skin surface via pores.
   b. Apocrine: activated at puberty; present in axillary, anal and genital regions; composed of
   true sweat and lipid and protein components.
3. Ceruminous: produce cerum, ear wax

Question 8

HAIR:

Answer 8

HAIR: present in thin skin only. Root hair plexuses contain sensory receptors. Arrector pili: smooth muscle
cells contract in response to stress.