The Integumentary System: An Overview

Transcription

1 The Integumentary System: An Overview

2 Functions: Protective covering Helps regulate body temperature Retards water loss from deeper tissues Houses sensory receptors Synthesizes biochemicals Excretes small quantities of waste

3 Consists of Cutaneous membrane Epidermis Dermis Accessory structures- hair, sweat glands, sebaceous glands etc. Subcutaneous layer (hypodermis)

4 Components Figure 5.1

5 The Epidermis

6 Epidermis The epidermis is composed of layers of keratinocytes- cells that produce keratin Figure 5.2

7 The Epidermis Composed of stratified squamous epithelium Lacks blood vessels Older cells are pushed to the top and harden in a process called keratinization.

8 Layers of the epidermis: From deep. Stratum basale/ germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum to superficial

9 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.

10 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

11 Melanocytes Figure 5.5a, b

12 Epidermal cells Synthesize vitamin D3 (cholecalciferol) when exposed to UV Aids in absorption of calcium and phosphorusneeded for bone strength

13 The Dermis

14 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

15 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

16 Stretch Marks Caused by excessive stretching of the dermis Patterns of collagen and elastic fibers form lines of cleavage

17 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

18 Hairs Composed of keratinized dead cells that are produced in hair follicles Project deep into the dermis and often into the hypodermis

19 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

20 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

21 Hair Color Produced by melanocytes at the hair papilla

22 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

23 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

24 Nails Keratinized cells that protects the tips of fingers and toes

25 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

26 Structure Contd. Lunula Pale crescent area near the root were blood vessels are absent