Exercize 7 Flashcards
Skin
Epidermis –
epithelium
➢ Dermis – underlying connective tissue
layer
Subcutaneous layer – also
called the hypodermis and is
NOT a technical part of the
skin.
Technically only two layers of ‘skin’ and the hypodermis.
EPIDERMIS
The epidermis has the following
features:
• Avascular – no blood vessels
• Keratinized stratified squamous
epithelium
• Contains 4 distinct cell types
• Contains 4 or 5 distinct layers
(depending on if it is thin skin or
thick skin)
EPIDERMAL LAYERS
In order from superficial to deep the
layers of the epidermis are:
• Stratum corneum
• Stratum lucidum (only in thick skin)
• Stratum granulosum
• Stratum spinosum
• Stratum basale
CELLS OF THE EPIDERMIS:
KERATINOCYTES
- Keratinocytes (approx. 95% of cells in the
epidermis)
➢ Fibrous protein keratin makes tissue tough
➢ Linked by desmosomes so cells hold together
➢ Mitotically and metabolically active only in the
deepest two layers due to blood supply
availability
➢ As the cells divide in the lower layers, older
cells get pushed up into the more superficial
layers.
➢ It takes 40-50 days for a keratinocyte to migrate
from the deepest layer, to the most superficial
layer of the epidermis, where it is then sloughed.
CELLS OF THE
EPIDERMIS CONT’D
- Melanocytes – cells that produce a pigment ranging
from orange, to brown, to black in color – called melanin.
● When melanocytes are exposed to UV light, this
increases melanin production.
● Melanin acts as a shield to the nucleus of keratinocytes in
the deeper layers, helping to prevent damage from UV
radiation.
➢ 3. Dendritic (Langerhans) Cells – phagocytic, and
help with immune function
➢ 4. Tactile (Merkel) epithelial Cells - oval shaped
cells which function as receptors in conjunction with sensory
nerve endings to detect light touch sensation.
● Abundant in areas specialized for touch such as
fingertips and lip
DERMIS
The dermis has the following features:
• Highly vascular
• Contains two distinct layers of connective
tissue
• Papillary dermis – more superficial and
composed of areolar connective tissue
• Reticular dermis – deepest skin layer
composed of dense irregular connective
tissue.
PAPILLARY DERMIS
20% of the dermis is the papillary layer.
➢ Houses tactile corpuscles which detect light touch
and distinguish shape and texture.
➢ Where the dermis meets the epidermis in this layer,
dermal folds are formed. These are called dermal
papillae (hence the name of this layer).
➢ The papillae house small capillary beds where
oxygen and nutrients leave the blood and diffuse
into the epidermis.
➢ Collections of papillae and collagen fibers form
epidermal ridges which enhance the gripping
ability of the hands and feet.
DERMOGRAPHY:
FINGERPRINTING
Epidermal ridges occur in genetically
determined patterns unique to individuals.
• Sweat glands lie along these ridges and
produce a film resulting in a fingerprint.
RETICULAR DERMIS
Dense irregular connective tissue makes this layer
up, including a lot of collagen and some elastic
fibers, lending strength to this tissue.
➢ The ground substance also includes lots of
proteoglycans which draw in water and give the skin
a firm appearance.
➢ Houses lamellar corpuscles which detect deep
pressure and strong vibrations.
➢ Sweat and sebaceous glands are found here.
➢ This layer of the dermis has the most abundant
blood supply,
ACCESSORY ORGANS -
NAILS
Derived from the epidermis.
• Mostly non-living material.
• The nails appear pink because of blood
supply in the underlying dermis.
ACCESSORY ORGANS -
HAIR
Hairs are found all over the body surface except for
thick-skinned areas, parts of external genitalia, the
nipples, and the lips.
• The region of hair that is visible is termed the hair shaft.
• The region of hair that is beneath the surface of the skin
is the hair root and is imbedded in a hair follicle.
• The hair shaft and root are made of three layers of
keratinized cells.
• Medulla
• Cortex
• Cuticle
ACCESSORY ORGANS – GLANDS
SEBACEOUS GLANDS
➢Oil glands, which produce sebum
– a combination of oil and cellular
fragments.
➢Most often empty into a hair
follicle, but some directly on skin
surface.
➢Highly active during puberty as a
result of increased hormones.
SWEAT GLANDS
➢ True exocrine glands which empty into
epithelial openings called pores.
➢ Categorized by the type of secretions:
➢ Eccrine sweat glands – produce a
clear secretion, primarily water, to
regulate body temperature.
➢ Apocrine sweat glands – same as
eccrine secretions with additional
proteins and fat-rich substances.
Located in axillary and genital regions.
INTEGUMENTARY
SYSTEM FUNCTIONS
The primary function of the skin, is
protection from:
• Mechanical trauma
• Pathogens
• Environmental hazards
• Radiation
• There are many other functions:
• Sensation
• Thermoregulation
• Excretion
• Vitamin D synthesis
