Skin and theSkin and the Integumentary Integumentary

SystemSystem

Types of MembranesTypes of Membranes A.A. SerousSerous membranes line body membranes line body cavities that lack openings to the cavities that lack openings to the outside.outside.

1.1. They line the thorax and They line the thorax and abdomen and cover the abdomen and cover the

organs organs within these cavities.within these cavities.2.2. Serous membranes are made Serous membranes are made

up of epithelium and loose up of epithelium and loose connective tissue and secrete connective tissue and secrete serous fluid that acts as a serous fluid that acts as a lubricant.lubricant.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

B.B. MucousMucous membranes line the membranes line the cavities and openings that lead to cavities and openings that lead to the outside of the body, including the outside of the body, including the oral and nasal cavities, and the oral and nasal cavities, and openings of the openings of the digestive,reproductive, digestive,reproductive, respiratory, and urinary systems.respiratory, and urinary systems.1.1. They consist of epithelium and They consist of epithelium and

connective tissue with connective tissue with specialized cells that specialized cells that

secrete secrete mucus. mucus.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

C.C. SynovialSynovial membranes line the membranes line the joint joint cavities.cavities.

1.1. These membranes These membranes consist of consist of only connective only connective tissues and tissues and they they secrete lubricating secrete lubricating synovial fluid.synovial fluid.

D.D. The The cutaneouscutaneous membrane consists membrane consists of the of the skin, skin, and is the subject and is the subject of the remainder of the remainder of this chapter.of this chapter.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Introduction:Introduction:A.A. Structural Organization of the Structural Organization of the

Organism. Chemicals, cells, Organism. Chemicals, cells, tissues, organs, and finally organ tissues, organs, and finally organ systems build the human body.systems build the human body.

B. Organs are body structures B. Organs are body structures composed of two or more different composed of two or more different tissues.tissues.

C.C. The skin (cutaneous membrane) The skin (cutaneous membrane) and its accessory organs make and its accessory organs make

up the integumentary system.up the integumentary system.

Skin and Its TissuesSkin and Its Tissues A.A. The skin is a large organ The skin is a large organ

responsible for: responsible for: 1.1. maintaining homeostasis through maintaining homeostasis through

temperature regulation, temperature regulation, 2.2. protection of underlying tissues, protection of underlying tissues, 3.3. retardation of water retardation of water loss, loss, 4.4. housing sensory receptors, housing sensory receptors, 5.5. synthesizing certain chemicals,synthesizing certain chemicals,6.6. excreting wastes.excreting wastes.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

B.B. The skin The skin consists of an consists of an outer outer epidermisepidermis and a and a dermisdermis, , connected to connected to underlying tissue underlying tissue by the by the subcutaneous subcutaneous layer layer (hypodermis).(hypodermis).

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

C.C. EpidermisEpidermis1.1. The epidermis is made up of The epidermis is made up of stratified stratified squamous epithelium and squamous epithelium and lacks blood lacks blood vessels.vessels.2.2. The layer of reproducing cells (the The layer of reproducing cells (the

stratum basale), which lies at the stratum basale), which lies at the base of base of the epidermis, is well-the epidermis, is well-nourished by nourished by dermal blood vessels.dermal blood vessels.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3.3. Cells are pushed outward as Cells are pushed outward as new new cells are formed, and cells are formed, and become become keratinized as they die. keratinized as they die. Four or five Four or five layers may be seen:layers may be seen:stratum basale, stratum basale, stratum spinosum, stratum spinosum, stratum stratum granulosum, and stratum granulosum, and stratum corneum corneum are always are always present present and the and the stratum lucidum is found in stratum lucidum is found in

the the thicker palms and soles.thicker palms and soles.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

4.4. The epidermis is important because The epidermis is important because it it protects against water loss, protects against water loss, mechanical injury, chemicals, and mechanical injury, chemicals, and microorganismmicroorganism

5.5. MelanocytesMelanocytes, which lie deep in the , which lie deep in the epidermis and underlying dermis, epidermis and underlying dermis, produce a pigment called melanin that produce a pigment called melanin that protects deeper cells from the sun'sprotects deeper cells from the sun'sultraviolet rays.ultraviolet rays.

6.6. Melanocytes pass melanin to nearby Melanocytes pass melanin to nearby cells through cytocrine secretion.cells through cytocrine secretion.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

D.D. Skin ColorSkin Color

1.1. Skin color results from a Skin color results from a combination combination of of genetic, genetic, environmental, and environmental, and physiological factors.physiological factors.

2.2. Genetic differences in skin color Genetic differences in skin color result result from differing amounts from differing amounts of melanin and of melanin and in the size of in the size of melanin granules. melanin granules.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3.3. Exposure to sunlight causes Exposure to sunlight causes darkening darkening of skin of skin

as melanin as melanin production production increases.increases.

4.4. Circulation within dermal blood Circulation within dermal blood vessels affects skin vessels affects skin

color. color.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

E.E. DermisDermis

1.1. The dermis binds the epidermis The dermis binds the epidermis to to underlying tissues. underlying tissues. Epidermal Epidermal ridges and dermal ridges and dermal papillae cause papillae cause the border to be the border to be uneven.uneven.

2.2. The dermis consists of connective The dermis consists of connective tissue with collagen and tissue with collagen and

elastic elastic fibers within a fibers within a gel-like gel-like ground ground substance. substance.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3.3. Dermal blood vessels carry Dermal blood vessels carry nutrients to upper layers of skin and nutrients to upper layers of skin and help to regulate temperature.help to regulate temperature.

4.4. The dermis also contains nerve The dermis also contains nerve fibers, sensory fibers, hair follicles, fibers, sensory fibers, hair follicles, sebaceous glands, and sweat glands. sebaceous glands, and sweat glands.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

F.F.Subcutaneous LayerSubcutaneous Layer

1.1. The subcutaneous layer The subcutaneous layer (hypodermis) is composed (hypodermis) is composed of loose connective tissue of loose connective tissue and insulating adipose and insulating adipose tissue.tissue.2.2. It binds the skin to It binds the skin to underlying organs and underlying organs and contains the blood vessels contains the blood vessels that supply the skin.that supply the skin.3.3. No sharp boundary exists No sharp boundary exists between the dermis and between the dermis and subcutaneous layer. subcutaneous layer.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Accessory Organs of the SkinAccessory Organs of the Skin

A.A. Hair FolliclesHair Follicles

1.1. Hair can be found in Hair can be found in nearly all nearly all

regions of the regions of the skin.skin.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2.2. Individual hairs develop Individual hairs develop from cells from cells at the base of the hair follicle, an at the base of the hair follicle, an invagination of the invagination of the lower epidermis lower epidermis that dips down into the dermis.that dips down into the dermis.

3.3. As new cells are formed, old cells are As new cells are formed, old cells are pushed outward and become pushed outward and become keratinized, and die forming the hair keratinized, and die forming the hair shaft. shaft.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

4.4. A bundle of smooth muscle cells, A bundle of smooth muscle cells, called the called the arrector pili musclearrector pili muscle, , attaches to each hair follicle. These attaches to each hair follicle. These muscles cause muscles cause goose bumps when goose bumps when cold or frightened.cold or frightened.

5.5. Hair color is determined by genetics; Hair color is determined by genetics; melaninmelanin from melanocytes is from melanocytes is responsible for most hair colors, but responsible for most hair colors, but red red hair also contains the hair also contains the pigment pigment trichosiderin. trichosiderin.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

B.B. Sebaceous Glands Sebaceous Glands

1.1. Sebaceous glandsSebaceous glands (holocrine (holocrine glands) are glands) are associated with associated with hair follicles and hair follicles and secrete sebum secrete sebum that waterproofs that waterproofs and and moisturizes moisturizes the hair the hair shafts. shafts.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

C.C. Nails Nails

1.1. Nails are protective coverings over the Nails are protective coverings over the ends of fingers and toes.ends of fingers and toes.

2.2. Nails consist of stratified squamous Nails consist of stratified squamous epithelial cells overlying the nail bed, with epithelial cells overlying the nail bed, with the lunula as the most actively growing the lunula as the most actively growing region of the nail root.region of the nail root.

3.3. As new cells are produced, older ones are As new cells are produced, older ones are pushed outward and become keratinized. pushed outward and become keratinized.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

D.D. Sweat Glands Sweat Glands 1.1. Sweat glands (sudoriferous glands)Sweat glands (sudoriferous glands) are either are either

eccrine, which respond to eccrine, which respond to body body temperature, or temperature, or

apocrineapocrine, which respond to body , which respond to body temperature, stress, and sexual arousal.temperature, stress, and sexual arousal.

2.2. Modified sweat glands, called Modified sweat glands, called ceruminousceruminous glands, secrete glands, secrete wax in wax in the the ear canal.ear canal.

3.3. Mammary glands, another modified type Mammary glands, another modified type of sweat glands, secrete milk.of sweat glands, secrete milk.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Regulation of Body TemperatureRegulation of Body Temperature

A.A. Proper temperature regulation is Proper temperature regulation is vital to vital to maintaining metabolic maintaining metabolic reactions.reactions.

B.B. The skin plays a major role in The skin plays a major role in temperature regulation with the temperature regulation with the hypothalamus controlling it.hypothalamus controlling it.

C.C. Active cells, such as those of Active cells, such as those of the the heart heart and skeletal muscle, and skeletal muscle, produce produce heat.heat.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Healing of Wounds and Healing of Wounds and BurnsBurns A.A. InflammationInflammation, in which blood , in which blood

vessels vessels dilate and become dilate and become more more permeable, permeable, causing causing tissues to tissues to become red and become red and swollen, swollen, is the is the body's normal response body's normal response to to

injury.injury.B.B. Superficial cuts are filled in Superficial cuts are filled in by by reproducing epithelial cells.reproducing epithelial cells.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

C.C. Deeper cuts are closed off Deeper cuts are closed off by clots, by clots, covered by scabs, and covered by scabs, and eventually eventually filled filled in by in by fibroblasts, making fibroblasts, making connective connective tissue. Blood vessels tissue. Blood vessels extend into extend into the the area, injured area, injured tissues are tissues are replaced, and replaced, and the the scab falls off.scab falls off.D.D. Large wounds leave scars Large wounds leave scars and and healing healing may be may be accompanied by accompanied by the formation the formation of of granulations.granulations.

CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.