The Integumentary System: An...
Transcript of The Integumentary System: An...
Functions:
� Protective covering � Helps regulate body temperature � Retards water loss from deeper tissues � Houses sensory receptors � Synthesizes biochemicals � Excretes small quantities of waste
Consists of…
� Cutaneous membrane � Epidermis � Dermis
� Accessory structures- hair, sweat glands, sebaceous glands etc.
� Subcutaneous layer (hypodermis)
Epidermis
� The epidermis is composed of layers of keratinocytes- cells that produce keratin
Figure 5.2
The Epidermis � Composed of stratified squamous epithelium � Lacks blood vessels � Older cells are pushed to the top and harden
in a process called keratinization.
Layers of the epidermis:
� Stratum basale/ germinativum � Stratum spinosum � Stratum granulosum � Stratum lucidum � Stratum corneum
From deep…….
…… to superficial
Epidermis Cell Layers � Germinative
� Basal cells (stem) are reproducing � Spinosum- spiny layer � Granulosum- grainy layer
� Stops dividing, start producing keratin � Lucidum
� The clear layer found only in thick skin � Corneum
� Exposed to surface and shed every 2 wks.
Skin color depends on… � Blood supply
� Interrupted blood supply leads to cyanosis- blue! � Carotene
� Orange-yellow pigment found in orange vegetables � Melanin
� Yellow-brown pigment � Protects us from UV radiation � Produced by melanocytes
Epidermal cells � Synthesize vitamin D3 (cholecalciferol) when
exposed to UV
� Aids in absorption of calcium and phosphorus- needed for bone strength
Dermal Organization � Located between epidermis and
subcutaneous layer
� Anchors accessory structures- hair follicles, sweat glands, blood vessels etc.
� Two components: � Outer papillary layer � Deep reticular layer
Layers of the Dermis
� Papillary layer � Areolar tissue � Contains blood vessels, lymphatics, sensory
nerves of epidermis
� Reticular layer � Dense irregular connetive tissue � Contains network of collagen and elastic
fibers to resist tension
Stretch Marks
� Caused by excessive stretching of the dermis
� Patterns of collagen and elastic fibers form lines of cleavage
Hypodermis
� Elastic areolar tissue and adipose tissue � Stabilizes skins position against
underlying organs and tissues � Shock absorber and insulator � Few capillaries and no vital organs � Subcutaneous injection is useful to
administer drugs
Hairs
� Composed of keratinized dead cells that are produced in hair follicles
� Project deep into the dermis and often into the hypodermis
Structures � Hair papilla
� Connective tissue containing capillaries and nerves
� Root � Anchors hair into skin
� Shaft � Part we see on the surface � Consists of three layers ○ Cuticle- overlapping shingle layer ○ Cortex- underlying layer- pigments ○ Medulla- core of hair
Structures Contd.
� Sebaceous Glands � Discharge oily substance into hair follicles � Inhibits growth of bacteria
� Arrector pili muscle � Pulls on follicle, forcing the hair to stand up � Cold or emotional states- goosebumps
Function of Hair � Head
� Protection from UV light � Cushion a light blow to head � Insulation
� Nostrils, ears, and eyes � Prevent entry of particles
� Sensory � Sensory nerve fiber at base of every hair
Exocrine Glands- Reach Outside � Sebaceous glands (Oil glands)
� Associated with hair � Secrete sebum, which lubricates and inhibits
bacteria growth � Acne- condition when they are clogged
� Sweat glands (Watery Glands) � 2 kinds ○ 1- hormonal- armpits, groin, nipples ○ 2- All over body
Structures � Nail Body
� Covers an area of the epidermis called the nail bed
� Nail Root � Where nail production occurs � Not visible on surface
� Cuticle � Portion of stratum corneum