Integumentary System

1. Integumentary System

2. Statistics • Covers the entire body. • Weighs between 9 to 11 lbs. • Thickness of skin in some areas can be from 1.5 to 4 mm thick. • Flexible yet tough. • The #1 defense from bacteria and fungi.

3. Hypodermis (Not technically part of the skin) • A.k.a. Superficial fascia. • Stores fat • Anchors the skin (loosely) • It is important that we understand that the hypodermis anchors skin down loosely because it allows some potential trauma to slide off of the body. • Hypodermis will thicken when we gain weight. (In women, thighs and breasts first, in men anterior abdomen)

4. Hypodermis

5. Hypodermis anchors skin loosely

6. Hypodermis thickening

7. Epidermis • The epidermis is made up of keritanized stratified squamous epithelium.

8. Cell Types: Keratinocytes • Keratinocytes: cells that produce keratin. • Keratin: fibrous protein that gives skin its protective properties.

9. Cell Types: Melanocytes • Melanocytes: synthesize melanin. Have a web-like appearance. Found in the deepest part of the epidermis. • Melanin is created by the melanocytes, shipped up to the keratinocytes through the spider-like arms of the melanocyte, and deposited in the side of the nucleus of the keratinocyte that faces towards the sun, which creates a barrier that protects the keratinocyte’s nucleus from UV damage.

10. Melanocytes

11. Cell Types: Epidermal dendritic cells • A.k.a. Langerhan’s cells • Spawn from bone marrow and work their way to the epidermis. • Key part of the immune system.

12. Langerhan’s cells

13. Cell Types: Tactile cells • A.k.a. Merkel cells • Very intimately close to Merkel discs that act as receptors for the touch sense. • Merkel cell carinoma 

14. Layers of the epidermis • Number of layers vary based on whether skin is thick or thin. • Thick: 5 layers • Thin: 4 layers

15. Thick Skin • Thick skin’s 5 layers: • Stratum basale • Stratum spinosum • Stratum granulosum • Stratum lucidum • Stratum corneum • Examples of thick skin • Covers palms of hands • Fingertips • Feet • *Stratum= layer • *Strata= layers

16. Thin skin • Thin skin’s 4 layers: • Stratum basale • Stratum spinosum • Stratum granulosum • Stratum corneum • Examples of thin skin: • Everywhere else

17. Stratum Basale • A.k.a. Basal layer • Deepest layer and attached to the dermis. • As these cells divide, they push the cells above them closer to the surface of the skin, and force the other layers to mature into fully formed keratinocytes faster.

18. Stratum spinosum • Several layers thick. Contains a web-like system of intermediate filament designed to resist tension. • Looks like prickly spiked balls.

19. Stratum granulosum • Thin layer (3-5 layers). • This is where the bulk of keratinization occurs. Each of the layers in this stratum will start to look very different. • Cells flatten; nuclei and organelles disintegrate. • Forms lamented and keratohyaline cells. • Keratohyaline cells: helps form keratine in the upper layers • Lamented cells: creates water resistant glycolipids that fill extracellular spaces in the cell.

20. Stratum lucidum • Consists of two clear flat dead cell layers. Uses keratin to bind together in a cable like array. (thick skin only)

21. Stratum corneum • Outermost layer. (20-30 cell layers thick) • Mostly all the cells of this layer are dead. Designed to be durable and take damaged. Seen most often flaking off as dandruff.

23. End of Epidermis

24. Dermis • Second major skin region. Made of strong connective tissue. • Contains connective tissue proper cell types: • Fibroblasts • Macrophages • Few mast cells • Few white blood cells

25. Major layers of the dermis • Papillary layer: • Made of areolar connective tissue. • Contains interwoven elastic and collagen fibers. • Contains heavy amounts of blood vessels. • The loose connections of the tissue allows free movement of defensive cells, like the WBCs and macrophages.

26. continued • The superior surface contains peg-like projections called dermal papillae. Others contain free nerve endings (pain receptors) and touch receptors called Meissner’s corpuscules. • On the hands and feet, papillae lay on ridges called dermal ridges. The dermal ridges have ridges on top of them called epidermal ridges. These ridges of skin are collectively called friction ridges. • Since sweat pores open on these crests, we will leave behind a small film of sweat on anything we touch. You know these as fingerprints.

27. Reticular layer • The deeper and thicker of the two layers. • Course, irregular cell arrangement, dense fibrous connective tissue. • The cutaneous plexus, a layer of blood vessels that give nutrients to this layer, are between this layer and the hypodermis.

28. continued • In certain areas, skin that has less dense regions of the collagen fibers will form what is called cleavage. • When surgeons make an incision parallel to these lines, the skin gapes less and heals faster.

29. continued • Flexure lines are dermal folds that occur near joints where the dermis is firmly anchored to deeper structures. (look at the creases on the palms of your hands) • The dermis is folded due to the fact that skin cannot slide enough to conform to the joints in your hands.

31. End of Dermis

32. Skin Color • Three major pigments make up the skin: • Melanin • Carotene • Hemoglobin

33. Melanin • Only one of the three pigments made in the skin. • Polymer of tyrosine amino acids. • Passed up from melanocytes to keratinocytes. • Found only in the deepest layers of the epidermis.

34. Melanin

35. Human skin color • Skin tone: • Darker skinned people are distributed more around the equator. This is due to more direct contact from the sun’s rays. • Their skin produces more melanin to protect their skin cells from harmful UV rays.

36. Carotene • Yellow-orange pigment found in certain plants like carrots. Accumulates in the stratum corneum, and in fatty layers of the hypodermis. • In asian people, the yellowish tint to their skin is due to varying levels of melanin and carotene.

37. Carotene

38. Hemoglobin • The pinkish hue of hemoglobin is most evident in Caucasian people due to the fact that they lack very much pigment, allowing the reddish tint of hemoglobin to shine through the skin. Heme group

39. End of skin color

40. Glands • Appendages (added attachment) of the skin, glands function to cool down the body and expel wastes.

41. Sudoriferous Sweat Glands • All over the skin’s surface with the exception of the nipples and part of the external genitalia.

42. There can be upwards of 3 million of these glands on a body. • When myoepithelial cells contract, they squeeze out the secretion and forces the sweat to the skin surface.

43. Eccrine sweat glands • A.k.a. merocrine sweat glands. • Most abundant on the palms of the hands, forehead, and soles of the feet. • The secretory part is deep in the dermis, and pores (channels) allow for secretions to be brought to the surface. • The secretion from eccrine glands are what we call sweat.

44. Contains small amounts of uric acid (also found in urine), which alters the pH of sweat to between 4-6. • Major role is to prevent overheating of the body.

45. Apocrine glands • Confined to the axillary (under arm) and anogential (genital region) areas. • Begin functioning around puberty.

46. Ceriminous glands • Modified apocrine glands. • Secrete sebum in the ear canal. • Mix with sebacous glands to form ear wax.

47. Mammary glands • Secrete milk. • Also included as a part of the female reproductive system.

48. Oil based glands

49. Sebaceous Glands (oil glands) • Branched alveolar glands. Found everywhere except the thick skinned parts of the hands and feet. • Most are found in hair follicles. • gland store oils, and become so stuffed with oil, it explodes! (holocrine gland) • Lipids plus cell fragments= sebum

50. What happens when sebaceous glands become clogged up? • If a sebaceous gland becomes clogged with sebum, the a whitehead may form. • If that material oxidizes and dries, then a blackhead is formed.