The skin is the largest organ of the integumentary system and has several important functions: protection, insulation, regulation of temperature and water, production of vitamin D, and detection of stimuli. It has two main layers - the epidermis and dermis. The epidermis contains keratinocytes that produce keratin and has several sublayers including the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. The dermis lies underneath and contains blood vessels, hair follicles, and glands. It regulates temperature and contains receptors for touch, pressure, and pain. The skin also contains melanocytes that produce melanin pigment and

1. Integumentary System Andrew McCaskill - ICS

2. Functions of the SkinProtection (first line of defense)Insulates and cushions underlying tissuePrevents water loss (except for times when we need to, i.e. sweating)Produces proteins involved in immunitySynthesizes vitamin DContains cutaneous sense organs (nervous system, touch and temp. regulation)

3. Basic StructureThe skin is composed of two basic layers (regions)..Epidermis – outermost layerDermis –underlying connective tissueThese two layers are cemented together.

4. Keratinocytes/KeratinMost epidermal cells contain keratin, a protein that helps keep the skin hydrated by preventing water evaporation. These cells can also absorb water, further aiding in hydration, and explaining why humans experience wrinkling of the skin on the fingers and toes ("pruning") when immersed in water for prolonged periods. In addition, this layer is responsible for the "spring back" or stretchy properties of skin. A weak glutenous protein bond pulls the skin back to its natural shape.

5. EpidermisLayers (from deep to superficial)Stratum basale(basal layer) –The stratum germinativum (or basal layer, stratum basale) is the deepest layer of the epidermis, a continuous layer of cells often described as one cell thick. The basal cells of this layer can be considered the "stem cells" of the epidermis, undifferentiated, proliferating, and creating daughter cells that migrate upward, beginning the process of differentiation.. At any given time this layer is participating in mitosis. Melanocytes are found here (pigmented portion of the skin) Stratum spinosum(spiny layer)-This layer is also referred to as the "spinous" or "prickle-cell" layer. Keratinization begins in the stratum spinosum.The Stratum Basale and Stratum Spinosum receive adequate nourishment (through diffusion) from the dermis, however, each layer superificial to the stratum spinosum are pushed away from nourishment and eventually die.

6. EpidermisStratum granulosum(granular layer)- In this layer, keratinocytes are now called granular cells, and secrete glycolipids which is a waterproofing fat.

7. Stratum lucidum(clear layer) –The stratum lucidum is a layer of the epidermis found only in palmoplantarskin (the thicker skin of the palms and soles). It is composed of three to five layers of dead, flattened, clear keratinocytes.Epidermis cont. LayersStratum corneum(horny layer) The stratum corneum is the outermost layer of the epidermis, composed of large, flat, polyhedral, plate-like envelopes filled with keratin, which is made up of dead cells that have migrated up from the stratum granulosum. From the Latin for horn-coloured layer, this skin layer is composed mainly of dead cells that lack nuclei. As these dead cells slough off on the surface, they are continuously replaced by new cells from the stratum basale. In the human forearm, for example, about 1300 cells/cm2/hr are shed and commonly accumulate as house dust. This outer layer that is sloughed off is also known as the stratum dysjunctum.

9. DermisTwo distinct regions..Papillary layer –The papillary dermis is the uppermost layer of the dermis, composed of fine and loosely arranged collagen fibers. Its superior surface is uneven (fingerlike projections) which forms the characteristic fingerprint of the finger. This layer provides the epidermis with nutrients. Pain and touch receptors are found here.Reticular layer- The reticular dermis is the lower layer of the dermis, composed of thick, densely packed collagen fibers, and the primary location of dermal elastic fibers (elasticity of skin). Contains blood vessels, sweat and sebaceous glands and pressure receptors.

10. Blood and Temp. RegulationWhen the body temperature is high, the capillaries in the reticular layer become engorged (swell) releasing excess heat externally from the body. When the body temperature is low, the capillaries constrict, thus conserving body heat internally.

11. Dermal ReceptorsThe Dermis has extensive nerve receptors (Meissner’s corpuscle, Pacinian corpuscle, and hair follicle receptors) that sense external conditions (pain, pressure, or temperature extremes) and transmit the message to the central nervous system (CNS).

12. Cutaneous Glands* Sebaceous (oil) glands-Sebaceous glands are microscopic glands in the skin which secrete an oily matter, called sebum, in the hair follicles to lubricate the skin and hair. In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles. An infection causes acne. Sweat (sudoriferous) glands - Sweat glands are exocrine glands, found in the skin , that are used for body temperature regulation. Eccrine glands -Eccrine glands (or merocrine glands) are found at virtually all sites on the human body. They produce clear liquid (perspiration), consisting of water, salts, and urea. Apocrine glands- Apocrine glands are found in axillary and genital areas, secrete a milky protein and fat substance. This mixture is an excellent source of nutrients for bacteria which produce body odor. East Asians have multiply fewer apocrine sweat glands compared to people of European or African descent, and it may be for this reason that they are less susceptible to body odor.

13. HairFollicle- A hair follicle is a part of the skin that grows hair by packing old cells together.RootShaftHair bulbArrectorpili -Arrectorespilorum (singular Arrectorpili) are tiny muscle fibers attached to each hair follicle, which contract to make the hairs stand on end, causing goose bumps.Arrectorespilorum are smooth muscle, not skeletal muscle, which explains why humans cannot voluntarily give themselves goose bumps.

14. Nails- Fingernails and toenails are made of a tough protein called keratin. Along with hair and teeth they are an appendage of the skin.Free edge- The part of the nail that extends past the finger, beyond the nail plate. There should always be a free edge present to prevent infections.Nail folds (cuticle)- A fold of hard skin overlapping the base and sides of a fingernail or toenail Nail Matrix- This is the only living part of the nail. It is situated behind and underneath the Nail Fold and produces protein keratin which makes up the Nail Plate.

15. MelanocyteThrough a process called melanogenesis, these cells produce melanin, which is a pigment found in the skin, eyes, and hair. There are typically between 1000 and 2000 melanocytes per square millimeter of skin. Melanocytes comprise from 5% to 10% of the cells in the basal layer of epidermis.

16. skin colorThe difference in skin color between fair people and dark people is due not to the number (quantity) of melanocytes in their skin, but to the melanocytes' level of activity.

17. MelanomaMelanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye. It is one of the less common types of skin cancer but causes the majority of skin cancer related deaths. Malignant melanoma is a serious type of skin cancer. It is due to uncontrolled growth of pigment cells, called melanocytes.

18. Different Colors?

20. Shades skin color

22. A&E skin color

23. A&E skin color

24. One Generation

25. 25

26. Skin tones – Nat. Geo.‘Yet with the effects of human migrations and cultural habits, people in one place can show tremendous variation in skin tone – like students from the Washington International Primary School.” ‘Unmasking Skin,’ Joel L. Swerdlow, National Geographic, Nov. 2002 p46-47.

27. Tower of Babel

28. Acts 17:26And hath made of one blood all nations of men for to dwell on all the face of the earth, and hath determined the times before appointed, and the bounds of their habitation;Acts 17:26

29. Punnit Square - grays

30. Punnit Square - grays

31. Punnit Square - grays

32. Eye Shapes

33. What the facts show is that there are differences among us, but they stem from culture, not race.Q 664 abcnewswww.abcnews.com, Science page, "We're all the same," 9/10/98Q 664

34. Biological Fact

35. Acts 17:26And hath made of one blood all nations of men for to dwell on all the face of the earth, and hath determined the times before appointed, and the bounds of their habitation;Acts 17:26

36. Races?

37. Biblical View Acts 17:26

38. Biblical View Acts 17:26

39. Biblical View Acts 17:26