integumentary system

• Describe the general structure of the integument • Identify the varied functions of the integument • Describe the structure and composition of the epidermal layers • Describe the organisation and function of the layers of the dermis. • Identify nerve and blood supply to the dermis.

integument

hair skin nails, sweat glands and sebaceous glands

largest organ (7-8% body weight)

cutaneous membrane layers

1. epidermis → stratified squamous epithelium, avascular

2. dermis → areolar and dense connective tissue

3. hypodermis → subcutaneous layer ( not part of the skin ) mainly adipose

identify the varied functions of the integument

1. protection

2. prevention of water loss

3. temperature regulation

4. metabolic regulation

5. immune defense

6. sensory reception

7. excretion/secretionn

epidermis characteristics

1. keratinized stratified squamous epithelium

2. 4-5 layers ( strata) depending on skin type

3. avascular ( no surrounding blood vessels)

epidermal strata

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum ( thick skin)

5. stratum corneum

epidermal strata

stratum basale

undergoes mitosis, one layer of cells

• cells:

  • keratinocytes → produces keratin

  • melanocytes → produces melanin, protect DNA from UV danage

  • tactile cells → sense touch

stratum spinosum

connected by desmosomes; helps in mechanical strength

stratum granulosum

contains keratohyalin granules 4 keratin production

stratum lucidum

only found in thick skin

transparent, protective layers

stratum corneum

dead keratinized cells providing an outer layer

dermis

lies between the epidermis, vascular

2 layers

1. papillary layer

2. reticular layer

papillary layer

• superficial, areolar ct

• dermal papillae containing capillaries for epidermal nutrition

• dermal papillae and epidermal ridges interlock, increasing the surface area between epidermis and dermis

• directly under stratum basale

reticular layer

dense irregular connective tissue

forms most of the dermis

• contains collagen bundles, blood vessels, glands and nerve endings

functions of dermis

• provides strength and elasticity ( via collagen)

• supplies nutrients and houses sensory structures

innervation

• nerve fibers r present in the dermis

  functions

  • tactile receptors

  • control blood flow

  • control glandular secretion

blood supply

epidermis: avascular, dermis: vascular

• important in controlling blood pressure

• vasodilation → releases heat by widening vessels, vasoconstriction → conserves heart by narrowing vessels

  • collagen bundles

  • blood vessels

  • nerve endings

hypodermis

subcatenous layer, deep/ not really part of integument

composed of areolar ct and adipose ct

functions

• protects underlying structures

• stores energy

• provides thermal insulation

epidermal derivatives

• hair

• exocrine glands

• nails