Chapter 5 Integumentary System Body Membranes Epithelial Membranes

Chapter 5 Integumentary System

Body Membranes • Epithelial Membranes – Cutaneous – Mucous – Serous • Connective Tissue Membranes – Synovial membranes

Cutaneous Membrane • Composed of keratinizing stratified squamous epithelium with an underlying layer of dense connective tissue. • Is exposed to air • Is a dry membrane

Serous Membranes: Serosa • Consists of simple squamous epithelial layer resting on a connective tissue basement membrane • Parietal layer touches the wall of the ventral body cavity. • Visceral layer covers the outside of the organ • Serous fluid is secreted by both layers and separates the layers.

Serous Membranes Three locations: – pericardium around heart – pleura around lungs – peritoneum in abdominal cavity around abdominal organs Diseases • Pleurisy – inflammation of the serous membranes that line the chest cavity and cover the lungs • Peritonitis – inflammation of the serous membranes in the abdominal cavity that line the walls and cover the abdominal organs

Mucous Membrane: Mucosa • Lines all body cavities open to the exterior • Produce mucus, a thick secretion that keeps the membranes soft and moist • Are adapted for absorption and secretion

Connective Tissue Membrane: Synovial Membranes • Line the fibrous capsules surrounding joints • All connective tissue; no epithelial layer • Provide a smooth surface • Produce synovial fluid • Line bursae and tendon sheaths which cushion joints.

Quick Check 1. What are the four main types of membranes in the body? 2. Which of the body’s membranes are types of epithelial membrane? 3. What fluid(s) are produced by each of the four main membrane types? 4. What is the function of each fluid?

Integumentary System: Skin Functions – Insulation – Waterproofing: keratin – Regulate heat loss: capillaries and sweat glands – Excretion: urea, salts, water – Synthesis of Vitamin D with the aid of UV – Sensation: touch, pressure, temperature and pain receptors

Structure of Skin: Layers • Epidermis: outer layer made of stratified squamous epithelium • Dermis: under layer made largely of connective tissue • Hypodermis: (subcutaneous tissue) – Made of adipose & areolar connective tissue types. – Anchors skin to underlying organs and acts as shock absorber.

Epidermis • Composed of 5 distinct layers • Keratinocytes: produce keratin – Provides protection for outer layer • Melanocytes: produce melanin – Melanin protects DNA from UV radiation – Freckles and moles: concentrated melanin

Dermal-Epidermal Junction • Specialized area between two primary skin layers

Dermis • Deeper and thicker layer • Composed primarily of connective tissue • Contains: – – nerve endings muscle fibers hair follicles sweat and sebaceous glands – many blood vessels

Dermis • Papillary layer characterized by parallel row of tiny bumps called dermal papillae • Ridges and grooves form pattern unique to each individual – Basis of fingerprinting – Improves grip • Reticular layer – filled with network of tough, interlacing, collagenous and stretchable fibers – Number of fibers decrease with age and contributes to wrinkling elastic

Accessory Structures • • Hair Nails Sweat glands Sebaceous glands

Hair and hair follicles • Lanugo - soft hair of the fetus and newborn • Follicle – specialized structures required for hair growth • Papilla – area from which hair growth begins • Shaft – visible part of hair • Arrector pili – specialized muscle that causes hair to stand up straight and produces “goose bumps”

Receptors • Specialized nerve endings make it possible for the skin to act as a sense organ • Tactile (Meissner) corpuscle – detects light touch • Lamellar (Pacini) corpuscle – capable of detecting pressure

Nails • Produced by epidermal cell over terminal ends of fingers and toes • Nail body – visible part of nail • Root – lies in a groove and is hidden by cuticle • Lunula – crescent shaped area nearest root • Nail bed may change color with change in blood flow

Sudoriferous(sweat) Glands • Eccrine – Most numerous and important – Produce perspiration or sweat which flows from pores on the skin surface – Function throughout life and aid in heat regulation • Apocrine – Found primarily in axilla around genitalia – Secrete a thicker secretion than eccrine perspiration – Breakdown of secretion by bacteria produces odor and skin

Sebaceous (oil) Glands • • • Sebum - mix of oily substances and fragmented cells. Increased quantities during adolescence Usually empty into a hair follicle Keeps skin soft and prevents brittle hair Sebum in sebaceous gland ducts may darken to form a blackhead

Quick Check 1. What are the two major layers of the skin? 2. Where in the skin would you find layers of dead, keratinized cells? 3. How is hair formed? 4. Where in the skin would you find sensory nerve receptors? 5. What do sudoriferous glands produce? 6. What do sebaceous glands produce?

52 epidermis 53 Stratum basale 54 dermis Nerve Root sheath 55 56 hypodermis

Skin Cancer Causes • Genetic predisposition • Sun’s UV radiation damages skin cell DNA, causing mistakes during mitosis

Squamous Cell Carcinoma • Common type of skin cancer • Slow growing • May metastasize or spread and invade other areas of the body • Begins as a hard, raised nodule that is usually painless

Basal Cell Carcinoma • Most common type • Usually appears on upper face • Originates in the base of the epidermis • Often appears as a small, raised lesion that erodes in the center to form a bleeding, crusted crater.

Malignant Melanoma • Most serious form • Spreading brown to black patch that metastasizes to blood or lymph nodes • Recognized by ABCD Rule – Asymmetry – Border irregularity – Color variation – Diameter greater than 6 mm

Functions Protection - the first line of defense against: – Infection by microbes – UV rays from the sun – Harmful chemicals – Cuts and tears

Functions Temperature regulation • Skin can release almost 3, 000 calories of body heat per day • Mechanisms of temperature regulation – Regulation of sweat secretion – Regulation of flow of blood close to the body surface

Functions Sensory organ – Skin functions as an enormous sense organ – Receptors serve as receivers for the body, keeping it informed of changes in its environment

Burns • Treatment and recovery or survival depend on total are involved and severity or depth of the burn • Body surface area is estimated using the “rule of nines” in adults • Body is divided into 11 areas of 9% each • Additional 1% of body surface area is around the genitals

Types of Burns • Partial thickness burns – 1 st degree - only epidermis is damaged. Not serious. – 2 nd degree - injury to epidermis and upper dermis • Blisters, red, painful • Regeneration occurs

1 st and 2 nd degree burns

Types of Burns • Third-degree or full thickness burn – Destroys full thickness of skin – May involve muscle and bone – Initially not painful as nerve endings are destroyed – Regeneration not possible; skin grafts require – Risk of infection is increased

Quick Check 1. What are the five most important functions of the skin? 2. Can you list some of the sensory stimuli that can be detected by the skin? 3. How can the amount of skin surface area covered by a burn be estimated?