Associate Professor: Dina A.A. Hassan Associate Professor: Dina A.A. Hassan -Associative professor in pharmacology -Pharmacology department -College of Pharmacy -Sattam Ben Abdulaziz University, Al Kharge

INTEGUMENTARY SYSTEM Dr Dina Allam Hassan

OBJECTIVES At the end of this lecture, you should be able to: -Define and enumerate the structure of the Integumentary system -Describe layers of the skin in details and function of each layer. - -Define and locate hypodermal layer and its related functions. -Discuss the structure and function of hair follicles, nail, sweet and sebaceous glans ( which are collectively called Skin Appendages).

The Integumentary System Integumentary system is the skin and the organs derived from it (hair, glands, nails) It is also one of the largest organs ◦Largest sense organ in the body Integument is skin STRUCTURE OF THE SKIN: STRUCTURE OF THE SKIN: Two distinct regions ◦Epidermis ◦Dermis ◦A fatty layer (hypodermis) lies deep to it

Skin Appendages Derived from epidermis but extend into dermis Include  Hair and hair follicles  Sebaceous (oil) glands  Sweat glands  Nails

Functions of Skin Protection ◦Cushions and insulates and is waterproof ◦Protects from chemicals, heat, cold, bacteria ◦Screens UV Synthesizes of vitamin D with UV Regulates body heat Prevents unnecessary water loss Sensory reception (nerve endings)

Structure of the skin Histologically the skin is formed of two distinct regions: 1- Epidermis 2- Dermis N.B: A fatty layer (hypodermis) lies deep to it

Epidermis and Dermis ◦Epidermis is avascular (no blood vessels) ◦Dermis is highly vascular (has blood vessels) ◦Epidermis receives nourishment from dermis ◦Cells far away from nourishment die

1-Epidermis Four types of cells ◦Keratinocytes – produce keratin (tough fibrous protein) Keratinized stratified squamous epithelium ◦Melanocytes - make dark skin pigment melanin ◦Merkel cells – associated with sensory nerve endings ◦Langerhans cells – macrophage-like dendritic cells Layers of keratinocytes(from deep to superficial) ◦Stratum basale or germinativum – single row of cells attached to dermis; youngest cells and actively divide by mitosis to form new cells which forms the more superficial layers ◦Stratum spinosum or spinous layer – spine is artifactual; it contains tonofilaments (bundles of protein) resist tension ◦Stratum granulosum or granular layer – layers of flattened keratinocytes producing keratin (hair and nails made of it also) ◦Stratum lucidum or clear layer-(present only on thick skin as palms and soles) ◦Stratum corneum or horny layer –it is a dead layer that appears as flat membrane filled with keratin. (cells dead, many layers thick)

FUNCTION OF KERATINOCYES : FUNCTION OF KERATINOCYES : Cell renewal and formation of keratin.

2- Dermis See next picture 1)This layer locates deeper to dermis 2)It is formed of strong connective tissue 3)It is rich supply in nerves and blood vessels. 4)This layer is formed of two layers (see next slides) ◦Papillary layer that includes dermal papillae and formed of areolar connective tissue that rich in connective tissue cells(fibroblast, macrophages, mast cells). ◦Reticular layer – “reticulum” under the papillary layer and formed of networks of collagen and reticular fibers. That is why it is called reticular layer FUNCTION OF DERMIS : FUNCTION OF DERMIS : It has a critical role in temperature regulation (rich in blood vessels)

* Dermis layers * * * Dermal papillae

Hypodermis * It is also called : 1-“Hypodermis” = that means below the skin 2-“Subcutaneous” = that means below the skin 3- “superficial fascia” “fascia” (Latin) =in anatomy it means sheet of connective tissue Structure of hypodermis: It is formed of fatty tissue FUNCTIONS OF HYPODERMIS : * it is formed of fatty tissue which stores fat * it anchors skin to the underlying structure

Skin color Three skin pigments ◦Melanin: the most important ◦Carotene: from carrots ◦Hemoglobin: the pink of light skin Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basale ◦Digested by lysosomes ◦Variations in color ◦Function of melanin : Protection from UV light vs vitamin D?

Nails 1- It is formed of hard keratin 2- it grows from nail matrix

Hair and hair follicles: complex * Hair papilla is connective tissue ________________ Hair bulb: epithelial cells surrounding papilla except 1- Hair and hair follicles are derived from epidermis and dermis 2- usually they are present everywhere except palms, soles, nipples, parts of genitalia

Functions of hair: Functions of hair: ◦Warmth – less in human than other mammals ◦Sense light touch of the skin ◦Protection - Especially in the scalp Parts hair: Parts hair: ◦Root imbedded in skin ◦Shaft projecting above skin surface Make up of hair Make up of hair – hard keratin Three concentric layers Three concentric layers ◦Medulla (core) ◦Cortex (surrounds medulla) ◦Cuticle (single layers, overlapping)

Types of hair Types of hair ◦Vellus: fine, short hairs ◦Intermediate hairs ◦Terminal: longer, courser hair Hair growth: Hair growth: averages 2 mm/week ◦Active: growing ◦Resting phase ◦shed Hair loss: Hair loss: ◦Thinning – age related ◦Male pattern baldness Hair color: Hair color: ◦Increase mount of melanin for black or brown colour; ◦ Distinct form of melanin for red colour ◦White: decreased melanin and air bubbles in the medulla

Sebaceous (oil) Glands These glands usually connected to hair follicles They are present in entire skin of the body(thin skin) except palms and soles (thick skin). FUNCTION : FUNCTION : - Produce sebum - Sebum is an Oily material that lubricates hair.

Sweat Glands - These glands present in the entire thin skin surface except nipples and part of external genitalia - In humans sweet gland are efficient ( but in animals only mammals have efficient sweet glands ) FUNCTION: FUNCTION: 1- Produce sweet in response to stress as well as heat 2- Prevent overheating

Use the following vocabulary to label the diagram : hair shaft, oil (sebaceous)gland, fat cells, erector pili muscle, blood vessels, nerve endings, epidermis, dermis, epithelial cells, hair follicle, sweat gland, connective tissue