Chapter 6 : Integumentary System

4 steps to regeneration...

1. Cut blood vessels bleed into the wound carrying clotting proteins and antibodies with it 2. A blood cots and temporarily patches the edges of the wound together 3. The cut blood vessels regeneration and grow in the wound, a soft mass deep in the wound becomes granulation tissue, which is a vascular connective tissue that initially forms in a healing wound. Macrophages within the wound begin to remove the clotted blood and Fibroblasts produce new collagen fibers 4. Epithelial regeneration of the epidermis occurs due to division of epithelial cells at the edge of the wound and these new epithelial cells migrate over the wound. The connective tissue is replaced by fibrosis

Functions of Hair

1. Protection 2. Heat Retention 3. Sensory Reception 4. Visual Identification 5. Chemical signal dispersal

Cuticle

A single cell layer around the cortex forms the cuticle, which coats the hair

Pilus

A single hair, or pilus, has the shape of a slender filament; it is composed of keratinized cells growing from hair follicles that extend deep into the dermis, often projecting into the underlying subcutaneous layer

Apocrine Sweat Glands

Apocrine sweat glands are coiled, tubular glands that release their secretion into hair follicles in the axillae, around the nipples, in the pubic region, and in the anal region. The secretion they produce is viscous and cloudy, and it contains both proteins and lipids that are acted upon by bacteria to produce a distinct, noticeable odor. (Underarm deodorant is designed to mask the odor while a deodorant with antiperspirant also helps prevent the formation of sweat.) These sweat glands become active and produce secretions beginning around puberty

Squamous cell carcinoma

Arises from keratinocytes in the stratum spinosum Lesions usually found on scalp, ears, lower lip, dorsum of hand Concave ulcers with elevated edges May metastasize

Ceruminous Glands

Ceruminous glands are modified apocrine sweat glands located only in thee external acoustic meatus (ear canal), where their secretion forms a waterproof earwax called cerumen (sē-rū′men). Both cerumen and the tiny hairs in the meatus help trap foreign particles or small insects and keeps them from reaching the eardrum. Cerumen also helps lubricate the external acoustic meatus and eardrum.

Malignant Melanoma

Deadly; aggressive growth and metastasis Arises from melanocytes, usually a preexisting mole Sunburns Asymmetry Difficult to cure

Anatomy of Nails

Each nail has a distal whitish free edge, a pinkish nail body, and a nail root, which is the proximal part embedded in the skin. Together, these parts form the nail plate. The nail body covers a layer of epidermis that is called the nail bed, which contains only the deeper, living cell layers of the epidermis. At the nail root and the proximal end of the nail body, the nail bed thickens to form the nail matrix, which is the actively growing part of the nail. The lunula is the whitish semilunar area of the proximal end of the nail body. It has a whitish appearance because a thickened stratum basale obscures the underlying blood vessels. Along the lateral and proximal borders of the nail, folds of skin called nail folds overlap the nail. The eponychium, also known as the cuticle, is a narrow band of epidermis extending from the margin of the nail wall onto the nail body. The hyponychium is a region of thickened stratum corneum over which the free nail edge projects

Hair Matrix

Hair production involves a specialized type of keratinization that occurs within the hair matrix, a structure at the base of the hair bulb

Fibrosis

If the organ is too severely damaged or its cells lack the capacity to divid, the body fills the gap with scar tissue produced by fibroblasts and is composed of primarily collagen. Some structural restoration occurs but functional actives are not!

Male pattern baldness

In males, the condition called male pattern baldness causes loss of hair from only some regions of the scalp rather than uniformly. It is caused by a combination of genetic and hormonal influences. The relevant gene has two alleles, one for uniform hair growth and one for baldness. The baldness allele is dominant in males and is expressed only in the presence of the high level of testosterone that is characteristic of men

Vasodilation

Increase of blood vessel lumen

Basal cell carcinoma

Most common type of cancer Least dangerous type, seldom metastasizes Originates in stratum basale First appears as small, shiny elevation "pearly edge"

Vasoconstriction

Narrowing of blood vessel lumen

Skin color is defined by...

Normal skin color results from a combination of the colors of hemoglobin, melanin, and carotene

Sebaceous Glands

Sebaceous glands are holocrine glands that produce an oily, waxy secretion called sebum that is usually discharged into a hair follicle and onto the hair itself. Sebum acts as a lubricant to keep the skin and hair from becoming dry, brittle, and cracked (The secretion of sebum is stimulated by hormones, especially androgens (male sex hormones). Sebaceous glands are relatively inactive during childhood; however, they are activated during puberty in both sexes, when the production of sex hormones increases)

Cortex

Several layers of flattened cells closer to the outer surface of the developing hair form the relatively hard

Stratum Spinosum

Several layers of polygonal keratinocytes, each time a keratinocyte stem cell in the stratum basale divides, a daughter cell is pushed toward the external surface from the stratum basale, while the other cell remains as a stem cell in the stratum basale. Once this new cell enters the stratum spinosum, it begins to differentiate into a non-dividing, highly specialized keratinocyte. Sometimes the deepest cells in this layer still undergo mitosis to help replace epidermal cells that exfoliate from the surface. The nondividing keratinocytes in the stratum spinosum attach to their neighbors by many intercellular junctions called desmosomes

Friction Ridges

The contours of the skin surface follow ridge patterns, varying from small conical pegs (in thin skin) to the complex arches and whorls found on the fingers (fingerprints), palms, soles, and toes. These ridges are formed from large folds and valleys of both dermis and epidermis. They help increase friction on contact, so that our hands can firmly grasp items and our feet do not slip when we walk barefoot

Stratum Basale

The deepest epidermal layer is a single layer of cuboidal to low columnar cells that is tightly attached to an underlying basement membrane that separates the epidermis from the connective tissue of the adjacent dermis. Three types of cells occupy the stratum basale

Innervation

The dermis of the skin has an extensive innervation, which refers to its distribution of nerve fibers. Sensory nerve fibers in the skin monitor stimuli in both the dermis and epidermis. Touch receptors (e.g., tactile corpuscles) detect stimuli such as pressure, vibration, and cold, and then initiate sensory input to the brain

Hair Papilla

The epithelium at the base of the bulb surrounds a small hair papilla, which is composed of a small amount of connective tissue containing tiny blood vessels and nerves

Epidermis

The epithelium of the integument is called the epidermis. It is a keratinized, stratified squamous epithelium. From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (found in thick skin only), and the stratum corneum. The first three strata listed are composed of living keratinocytes, whereas the most superficial two strata contain dead keratinocytes

Integumentary System

The integumentary system consists of the skin and its derivatives: nails, hair, sweat glands, and sebaceous (oil) glands. We are most conscious of this highly visible body system because it characterizes our self-image and reflects our emotions. Our skin is a barrier to the outside world and is subjected to trauma, harmful chemicals, pollutants, microbes, and damaging sunlight. It usually remains strong and pliable, is easily cleaned, is self-renewing, and is a visual indicator of our physiology and health. Changes in the color of the skin may reflect body disorders or anomalies; skin changes or lesions sometimes reflect systemic infections or disease. The scientific study and treatment of the integumentary system is called dermatology

Lines of Cleavage

The majority of the collagen and elastic fibers in the skin are oriented in parallel bundles at specific body locations. The alignment of fiber bundles within the dermis is a result of the direction of applied stress during routine movement; therefore, the function of the bundles is to resist stress

Mammary Glands

The mammary glands of the breasts are modified apocrine sweat glands. Both males and females have mammary glands, but these glands only become functional in pregnant and lactating females, when they produce milk, a secretion that nourishes offspring

Epidermal Derivatives

The nails, hair, and exocrine glands of the skin all are derived from the epidermal epithelium. These structures also are known as epidermal derivatives, or appendages, of the integument

Exocrine glands of the skin

The skin houses many types of exocrine glands. The two most common types of exocrine glands are sweat (sudoriferous) glands and sebaceous glands

Sweat glands

The two different groups of sweat glands in the skin are merocrine (eccrine) sweat glands and apocrine sweat glands. Both have a coiled, tubular secretory portion that is located in the reticular layer of the dermis, and a sweat gland duct that carries the secretion to the surface of the epidermis (in a merocrine gland) or into a hair follicle (in an apocrine gland). The opening of the sweat gland duct on the epidermal surface is an indented region called a sweat pore

Subcutaneous layer

This layer consists of both areolar connective tissue and adipose connective tissue. In some locations of the body, adipose connective tissue predominates, thus the subcutaneous layer is called subcutaneous fat. The connective tissue fibers of the reticular layer of the dermis are extensively interwoven with those of the subcutaneous layer to stabilize the position of the skin and bind it to the underlying structures. The subcutaneous layer pads and protects the body, acts as an energy reservoir, and provides thermal insulation

Striae

When the skin is stretched beyond its capacity, some collagen fibers are torn and result in stretch marks, called striae

Vitamin D3

also called cholecalciferol, is synthesized by keratinocytes when exposed to ultraviolet radiation and is later converted into calcitriol which balances our absorption of calcium and phosphates (10-15 minutes of sunlight is all thats needed daily!)

Cavernous Hemangiomas

also known as port-wine stains, involve larger dermal blood vessels and may last a lifetime

Tactile Cells

are few in number and found scattered among the cells within the stratum basale. Tactile cells are sensitive to touch and, when compressed, they release chemicals that stimulate sensory nerve endings, providing information about objects touching the skin

Epidermal Dendritic Cells

are immune cells that help fight infection in the epidermis. These immune cells are often present in the stratum spinosum and stratum granulosum, but they are not identifiable in standard histologic preparations. Their phagocytic activity initiates an immune response to protect the body against pathogens that have penetrated the superficial epidermal layers as well as epidermal cancer cells

Keratinocytes

are the most abundant cell type in the epidermis and are found throughout all epidermal strata. The stratum basale is dominated by large keratinocyte stem cells, which divide to generate new cells that replace dead keratinocytes shed from the surface. Their name is derived from their synthesis of keratin, a protein that strengthens the epidermis considerably

Merocrine Sweat Glands

are the most numerous and widely distributed sweat glands. They are simple, coiled tubular glands that discharge their secretions directly onto the surface of the skin. The clear secretion they release by exocytosis is called sweat; it consists of approximately 99% water and 1% other chemicals that include electrolytes. The major function of merocrine sweat glands is thermoregulation, which is the regulation of body temperature by evaporation of fluid from the skin. Merocrine sweat gland secretions provide a means for the loss of both water and electrolytes

Freckles

are yellowish or brown spots that represent localized areas of increased melanocyte activity, not an increase in melanocyte numbers. A freckle's degree of pigmentation varies and is dependent upon both sun exposure and heredity

a Nevus

commonly called a mole, is a harmless localized overgrowth of melanin-forming cells. On rare occasions, a nevus may become malignant, typically as a consequence of excessive UV light exposure

Hair bulb

consists of epithelial cells and is a swelling at the base where the hair originates in the dermis

Stratum Granulosum

consists of three to five layers of keratinocytes superficial to the stratum spinosum. Within this stratum begins a process called keratinization, where the keratinocytes fill up with the protein keratin, and in so doing, cause both the cell's nucleus and organelles to disintegrate and the cell starts to die. Keratinization is not complete until the cells reach the more superficial epidermal layers. A fully keratinized cell is dead (because it has neither a nucleus nor organelles), but it is structurally strong because of the keratin it contains

Thin skin

covers most of the body. It lacks a stratum lucidum, so it has only four specific layers in the epidermis. Thin skin contains the following structures: hair follicles, sebaceous glands, and sweat glands. The epidermis of thin skin ranges from 0.075 mm to 0.150 mm thick

Transdermal Administration

drugs that are soluble either in oils or lipid-soluble carries may be administered transdermally by an adhesive patch that keeps the drug in contact with the skin surface

Arrector pili

extending from the hair follicle to the dermal papillae are thin ribbons of smooth muscle that collectively are called the arrector pili

Reticular layer

forms the deeper, major portion of the dermis that extends from the papillary layer to the underlying subcutaneous layer. The reticular layer consists primarily of dense irregular connective tissue through which large bundles of collagen fibers project in all directions. These fibers are interwoven into a meshwork that surrounds structures in the dermis, such as the hair follicles, sebaceous glands and sweat glands, nerves, and blood vessels. The word reticular means "network" and refers to this meshwork of collagen fibers

Melanocytes

have long, branching processes and are scattered among the keratinocytes of the stratum basale. They produce and store the pigment melanin in response to ultraviolet light exposure. Their cytoplasmic processes transfer pigment granules, called melanosomes, into the keratinocytes within the basal layer and sometimes in more superficial layers. This pigment (which includes the colors black, brown, tan, or yellow-brown) accumulates around the nucleus of the keratinocyte and shields the nuclear DNA from ultraviolet radiation. The darker tones of the skin result from melanin produced by the melanocytes

Diffuse hair loss

is a condition where hair is shed from all parts of the scalp. Women primarily suffer from this condition, which may be due to hormones, medications, or iron deficiency

Lanugo

is a fine, unpigmented, downy hair that first appears on the fetus in the last trimester of development

Melanin

is a pigment produced and stored in melanocytes, and occurs in a variety of black, brown, tan, and yellow-brown shades as mentioned earlier. Recall that melanin is transferred in vesicles from melanocytes to keratinocytes in the stratum basale. Because keratinocytes are displaced toward the stratum corneum, melanocyte activity affects the color of the entire epidermis

Stratum Lucidum

is a thin, translucent region of about two to three cell layers that is superficial to the stratum granulosum. This stratum is found only in the thick skin within the palms of the hands and the soles of the feet. Cells occupying this layer appear pale and featureless and have indistinct boundaries. The keratinocytes within this layer are flattened and filled with the translucent protein called eleidin, which is an intermediate product in the process of keratin maturation. This layer helps protect the skin from ultraviolet light

Carotene

is a yellow-orange pigment that is acquired from various yellow-orange vegetables, such as carrots, corn, and squashes. Normally, it accumulates inside keratinocytes of the stratum corneum and in the subcutaneous fat. Within the body, carotene is converted into vitamin A, which plays an important role in normal vision. Vitamin A has also been thought to reduce potentially dangerous molecules called free radicals that form during normal metabolic activity in the body. Additionally, carotene may improve immune cell number and activity

Hemangioma

is an anomaly that results in skin discoloration due to blood vessels that proliferate to form a benign tumor

Hair follicle

is an oblique tube that surrounds the hair root. It always extends into the dermis and sometimes into the subcutaneous layer. The cells of the follicle walls are organized into two principal concentric layers: an outer connective tissue root sheath, which originates from the dermis; and an inner epithelial tissue root sheath, which originates from the epidermis

Hemoglobin

is an oxygen-binding protein present in red blood cells. It exhibits a bright red color upon binding oxygen, thus giving blood vessels in the dermis a reddish tint that is seen most easily in lightly pigmented individuals. If the blood vessels in the superficial layers vasodilate (in other words, the blood vessel diameter increasess), such as during physical exertion, then the red tones are much more visible

Dermis

is deep to the epidermis and ranges in thickness from 0.5 mm to 3.0 mm. This layer of the integument is composed of connective tissue proper, and contains primarily collagen fibers, although both elastic and reticular fibers also are found within the dermis

Hair

is found almost everywhere on the body except the palms of the hands and palmar surface of the fingers, the sides and soles of the feet and toes, the lips, and portions of the external genitalia

Thick skin

is found on the palms of the hands, the soles of the feet, and corresponding surfaces of fingers and toes. All five epidermal strata occur in the thick skin. The epidermis of thick skin ranges between 0.4 mm and 0.6 mm thick. It houses sweat glands but has no hair follicles or sebaceous (oil) glands

Hair shaft

is that portion of the hair that extends beyond the skin surface. The hair bulb contains living epithelial cells, while the root and shaft consist of dead epithelial cells

Stratum Corneum

is the most superficial layer of the epidermis. It is the stratum you see when you look at your skin. The stratum corneum consists of about 20 to 30 layers of dead, scaly, interlocking keratinized cells. The dead cells are anucleate (lacking a nucleus) and are tightly packed together

Hair root

is the portion of the hair deep to the skin surface

Vellus

is the primary human hair and is found on the upper and lower limbs

Papillary layer

is the superficial region of the dermis that is found directly adjacent and internal to the epidermis. It is composed of areolar connective tissue, and it derives its name from the projections of the dermis called dermal papillae. The dermal papillae interdigitate with deep projections of the epidermis called epidermal ridges. Together, the epidermal ridges and dermal papillae increase the area of contact between the two layers and interlock them

Alopecia

is the thinning of hair

Terminal Hair

is usually coarser, pigmented, and longer than vellus. It grows on the scalp, and it is also the hair of eyebrows and eyelashes. At puberty, terminal hair replaces vellus hair in the axillary and pubic regions, and it forms the beard on the faces of males

Medulla

not found in all hair types, is a remnant of the soft core of the matrix. It is composed of loosely arranged cells and air spaces, and contains flexible, soft keratin

Selective Permeability

some materials are able to pass through the skin and others are effectively blocked

Capillary Hemangiomas

strawberry-colored birthmarks, appear in the skin as bright red to deep purple nodules that are usually present at birth and disappear in childhood

Regeneration

the replacement of damaged or dead cells with the same cell type, this restores organ function