UNIT 2: Integumentary System

UNIT 2: Integumentary System

TISSUES!!

•Groups of cells that are similar in structure & perform a common or related function

–tissu = woven

•4 primary types that interweave to form the “fabric of the body”:

1. Epithelial (covering)

2. Connective (support)

3. Muscle (movement)

4. Nervous (control)

SKIN: INTEGUMENTARY SYSTEM

Functions of the Skin:

1.  ______

2.  ______(non-specific immunity)

3.  Retards (slows) ______

4.  Excretes ______

5.  Holds ______(pain, touch,..)

6.  Synthesis of biochemicals (ex:Vitamin D)

•The skin is the largest organ in the body

•Cool Facts:

-skin surface can be as large as 17-20 ft

-anywhere from 1/50 in. to 1/8 in. thick

•Together with its accessory organs, it constitutes the Integumentary System

• Skin is divided into 2 main distinct layers:

and separated by a

BASEMENT MEMBRANE (anchors epidermis to dermis)

à epidermis is subdivided into several layers

.

•There is also a distinct 3rd layer beneath the dermis called the ______

-binds skin to underlying tissues

Before we get to the epidermal layers… the cells of the Epidermis:

1. ______ - produce keratin (fibrous protein that helps give epidermis its protective properties

–

– through mitosis & are pushed to the surface

–Are ______by the time they reach the surface

2. ______ - produce ______

–Transfer melanin to nearby epidermal cells (keratinocytes)

SKIN COLOR:

• all people have about the same concentration of melanocytes;

• where we differ is in the amount and distribution of melanin

• environmental (sun exposure) and physiological factors, as well as GENES, influence skin color

Three pigments contribute to skin color:

–______– yellow to reddish-brown to black pigment, responsible for dark skin colors

•Freckles and pigmented moles à result from local accumulations of melanin

–______– yellow to orange pigment, most obvious in the palms and soles of the feet

–______– reddish pigment responsible for the pinkish hue of the skin (located within red blood cells; binds oxygen)

3.Langerhans cells-

–arise in bone marrow & migrate to the epidermis

NOW WE CAN LEARN ABOUT the layers of the epidermis!

•The epidermis is the most superficial layer of the skin and provides the first barrier of protection from the invasion of foreign substances into the body (such as?…)

The epidermis is avascular. What does that mean?

The EPIDERMIS is subdivided into five layers or strata from the bottom they are:

1. Stratum basale or Stratum germinativum (basal layer)

2. Stratum spinosum (prickly layer)

3. Stratum granulosum (granular layer)

4. Stratum lucidum (clear layer)

5. Stratum corneum (horny layer)

1. stratum germinativum (Stratum basale)

• provides the germinal cells (germinate: to start growing) necessary for ______

______

•These germinal cells are separated from the dermis by a thin layer of basement membrane.

•Germinal cells undergo mitotic division & then a progressive maturation called ______as they migrate to the surface.

2. stratum spinosum (prickly layer)

•Several cell layers thick

•When skin is prepared for histological studies, these cells shrink until they have a spiny appearance

•Cells with melanin granules and Langerhans’ cells are abundant in this layer

3. stratum granulosum (granular layer)

•3-5 cell layers

•Keratinocyte appearance changes

àaccumulate keratin granules that contain glycolipids which help to ______

______

4. stratum lucidum (clear layer)

•Appears as a thin translucent band

•May be absent in some areas of the skin

•Consists of a few rows of clear, flattened, dead keratinocytes with indistinct boundaries

•______and represents a transition from the stratum granulosum to the stratum corneum.

5. Stratum Cornium (horny layer)

•______

•20-30 cell layers thick; ______

•The dead and dying cells are ______(protection against abrasion & water loss!)

•These cells are pushed to the surface by newly forming cells of the stratum ______and the dead cells gradually break apart and are lost. (You’ve seen dandruff right?)

The Epidermis varies in thickness throughout the body depending mainly on frictional forces and is thickest on the palms of the hands and soles of the feet.

DERMIS:

• strong, flexible connective tissue layer

-contains fibroblast cells which secrete ______

______

• ______are scattered throughout the dermis

-some carry impulses to muscles and glands of the skin

-some are associated with sensory receptors and carry impulses to the brain and spinal cord

• contains ______, ______, and ______

• ______

SUBCUTANEOUS LAYER or HYPODERMIS:

• lies ______the dermis; consists of ______

______

• adipose tissue helps conserve body heat

• subcutaneous layer ______that supply the skin and adipose tissue