A&P 1 Exam 2 Study Guide complete 2023.
,A&P 1 Exam 2 Study Guide complete 2023.
INTEGUMENTARY SYSTEM: consists of the skin, hair, nails, and their associated
glands
The skin is the body’s largest and heaviest organ
It covers an area of 1.5 to 2.0m2 and accounts for 8% of body weight
Consists of two layers:
o Stratified squamous epithelium – epidermis
o Deeper connective tissue – dermis
Under the dermis is another connective tissue layer, the hypodermis
THICK SKIN: covers the palms, soles, and corresponding surfaces of the
fingers and toes
o Thick due to a very thick surface layer of dead cells called the stratum
corneum
o Has sweat glands but no hair follicles or sebaceous glands
o 5 STRATUM
THIN SKIN: has a thin epidermis with a thin stratum corneum
o Possesses hair follicles, sebaceous glands, and sweat glands
o 4 STRATUM
FUNCTIONS OF THE SKIN
1. Resistance to trauma and infection – resists and recovers from trauma
better than any organ, epidermal cells are packed with keratin a tough
protein and linked by strong desmosomes that give durability.
2. Barrier functions – important barrier to water, prevents the body from
absorbing excess water and prevents the body from losing excess water.
Also, a barrier to UV rays, blocking much of cancer-causing radiation from
going deeper tissue layers. Permeable to several drugs and poisons.
3. Vitamin D synthesis – skin carries out the first step in the synthesis of
vitamin D, needed for bone development and maintenance
,A&P 1 Exam 2 Study Guide complete 2023.
4. Sensation – most extensive sense organ, equipped with nerve endings that
react to heat, cold, touch, texture, pressure, vibration, and tissue injury.
Receptors are abundant on the face, palms, fingers, soles, nipples; few on
the back and skin over joints.
5. Thermoregulation – thermoreceptors monitor the body surface
temperature. In response to chilling, the body retains heat constricting
blood vessels of the dermis. In response to overheating, it loses excess heat
by dilating blood vessels. Evaporation of sweat can have a powerful cooling
effect
6. Nonverbal communication
EPIDERMIS
EPIDERMIS: keratinized stratified squamous epithelium that’s surface is consists
of dead cells packed with tough protein keratin
o Lacks blood vessels
o Depends on the diffusion of nutrients from underlying connective
tissue
o Sparse nerve endings for touch and pain
CELLS OF THE EPIDERMIS
o Keratinocytes: great majority of epidermal cells, named for their role
in synthesizing keratin. Nearly all visible epidermal cells
o Stem cells: undifferentiated cells that divide and give rise to
keratinocytes, found in only in stratum basale, deepest layer of
epidermis
o Melanocytes: also, in the stratum basale, synthesize the brown to
black pigment, melanin.
o Tactile cells: relatively few in number, are receptors for touch. Found
in the basal layer of the epidermis and are associated with dermal
nerve fiber, collectively called tactile disc
o Dendritic cells: found in two layers of the epidermis called the
stratum spinosum and stratum granulosum. Immune cells that
originate in bone marrow, stand guard against toxins, microbes, and
other pathogens that penetrate into the skin. Send defense signals.
, A&P 1 Exam 2 Study Guide complete 2023.
LAYERS OF THE EPIDERMIS
o Stratum Basale
Single layer of cuboidal to low columnar stem cells and
keratinocytes resting on the basement membrane
Also includes melanocytes, tactile cells, and stem cells
o Stratum Spinosum
Consists of several layers of keratinocytes and dendritic
cells
In most places, thickest stratum
Produce more keratin filaments which cause the cells to
flatten
o Stratum Granulosum
Consists of three to five layers of flat keratinocytes
The keratinocytes of this layer contain coarse, dark-staining
keratohyalin granules
o Stratum Lucidum
Thin zone that is seen only in thick skin
Keratinocytes are densely packed with clear protein called
eleidin
No nuclei or other organelles, pale and featureless
o Stratum Corneum
Consists of up to 30 layers of dead, scaly, keratinized cells
that form a durable surface layer
Resistant to abrasion, penetration, and water loss
DERMIS
DERMIS: a connective tissue layer that ranges from 0.2 mm thick and composed
mainly of collagen, but also contains elastic and reticular fibers, fibroblasts, and
other cells typical of fibrous connective tissue
o Supplied with blood vessels, cutaneous glands, and nerve endings
o Hair follicles and nail roots are embedded in the dermis
o In the face, skeletal muscles attach to dermal collagen fibers and produce expressions
