SSN Session

SkinJennifer Chang (jtc2109)

Bram Welch-Horan (tbw5)October 19, 2005

• Protection - barrier to outside environmentabrasion, moisture, UV light, microorganisms

• Homeostasis - maintenance of internal environmenttemperature, water and salts

• Sensation touch, temperature, pain, pressure, vibration

• Immune surveillance Langerhans’ cells – type of macrophage

• Endocrine function synthesizes vitamin D

Functions

Hairy Glabrous

Types of SkinThick – covers palms of hands and soles of feet, glabrousvs.Thin – covers rest of body, mostly hairy

3 layers

• Epidermis

stratified squamous keratinizing epithelium

• Dermis

papillary layer of loose connective tissue underlain by dense irregularly arranged CT

• Hypodermis

aka subcutaneous tissue, loose CT, contains adipose tissue

Epidermis – stratified squamous keratinized epithelium

5 Layers

1. Stratum corneum

2. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basalis

Stratum corneum

• Superficial keratinized layer• Cells have no nuclei or

organelles• Sealed extracellular space• Most superficial cells are

sloughed off

Stratum granulosum

• Basophilic granules of keratohyalin – Promotes aggregation of

keratin filaments into tonofibrils• Lamellar bodies – water barrier

Stratum corneum

Stratum Spinosum

• several cell layers thick• attached by intercellular bridges (desmosomes)• cells artificially pulled apart, the attachment sites give spiny appearance• Langerhans’ cells found here

desmosomes

Stratum Basalis

mitotic cellcells with melanin

• Mitotic cell layer, attaches to basement membrane via hemidesmosomes

• Cells containing melanin may be either melanocytes or keratinocytes

• Melanin

- pigment - protection from UV rays

- synthesized in melanocytes using tyrosinase - taken up by keratinocytes

Question 1

In the stratum basalis, ______ are found. They attach keratinocytes to ______.

a. Hemidesmosomes, basal lamina

b. Desmosomes, basal lamina

c. Hemidesmosomes, other keratinocytes

d. Desmosomes, Langerhans cells Lab 8, slide 2

Question 1

In the stratum basalis, ______ are found. They attach keratinocytes to ______.

a. Hemidesmosomes, basal lamina

b. Desmosomes, basal lamina

c. Hemidesmosomes, other keratinocytes

d. Desmosomes, Langerhans cells Lab 8, slide 2

Question 2

Which of the following regarding these cells is true?

a) They are mitoticb) They do not have

organellesc) They contain

keratohyalin granulesd) They synthesize

melanin

Question 2

Which of the following regarding these cells is true?

a) They are mitoticb) They do not have

organellesc) They contain

keratohyalin granulesd) They synthesize

melanin

Question 3

This brown substance is synthesized in which cell layer?

a)Stratum corneumb)Stratum

granulosumc)Stratum spinosumd)Stratum basalis

Question 3

This brown substance is synthesized in which cell layer?

a)Stratum corneumb)Stratum

granulosumc)Stratum spinosumd)Stratum basalis

Specialized Structures in Skin

• Nerve supply

• Hair follicles

• Sweat glands

• Sebaceous glands

• (Nails)

• (Mammary glands)

(http://www.columbia.edu/~johan/images/arm.jpg)

The Dermis• Papillary layer

– loose CT– bv’s, nerves,

lymphatics– papillae into

epidermis– Meissner’s

corpuscles

• Reticular layer– dense CT (less

cellular)– eccrine sweat glands– Pacinian corpuscles– anatomy: Langer’s

lines

(Ross, 4/e, p. 425)

Cutaneous Nerve Endings

• (Free nerve endings)– pain & temperature

• (Merkel’s cells)– high-res. tactile sensation (in stratum basale)

• Meissner’s Corpuscles– touch

• Pacinian Corpuscles– vibration & pressure

(Skin lab, slide 16; Cajal stain)

Meissner’s Corpuscles

• in dermal papillae (papillary layer of dermis)

• mechanoreceptors• 2-point

discrimination• encapsulated

• CT capsule• contrast w/ free

nerve endings (Ross, 4/e, p. 412)

Pacinian Corpuscles

(Ross, 4/e, p. 431)

Pacinian Corpuscles

• in deeper dermis & hypodermis– reticular layer

• vibration & pressure• encapsulated• characteristic appearance

– “onion” / “bull’s eye”

• diagnostic for dermis– or hypodermis

• hypodermis – loose CT, bv’s, fat, etc.– a.k.a., subcutaneous tissue,

superficial fascia(Skin lab, slide 18)

Hair Follicles

• epithelially derived– epidermal invagination– matrix of follicle equiv.

to stratum basale

• most of body surface• body temp. regulation• sebaceous glands

– secrete into follicle

• arrector pili– smooth muscle – “goosebumps”– assists gland secretion

(Ross, 4/e, p. 414)

Sebaceous Glands

• associated w/ hair follicle• secrete sebum between

shaft & follicle• holocrine secretion

– oil-filled cells apoptose– secretory product & cell

debris discharged from gland

• sebum may be protective– but is involved in acne

(Skin lab, slide 21)

• coiled tubular glands in dermis (reticular layer)– not associated with hair follicles; widely distributed

• secretory portion (w/ basal lamina)• myoepithelial cells

– contract expel sweat

• ducts – cuboidal cells– stratified (2 layers)– corkscrew path

– reabsorb H2O, salt

• sweat is hypotonic– contains H2O, salt, IgA

• temp. regulation

Eccrine Sweat Glands

(Skin lab, slide 13)

Sweat Ducts

(Skin lab, slide 12)

Question 4

• What is the function of this nerve ending, and which skin layer is it in?

a) pain; hypodermisb) temp.; reticular layerc) two-pt.

discrimination; papillary layer

d) itch; epidermis

(Skin lab, slide 15)

Question 4

• What is the function of this nerve ending, and which skin layer is it in?

a) pain; hypodermisb) temp.; reticular layerc) two-pt.

discrimination; papillary layer

d) itch; epidermis

(Skin lab, slide 15)

Question 5

• The product of the gland in this image would most likely be:

a) attractive to a potential mate

b) hypotonicc) mainly waterd) oily and associated

with cell debris (Skin lab, slide 23)

Question 5

• The product of the gland in this image would most likely be:

a) attractive to a potential mate

b) hypotonicc) mainly waterd) oily and associated

with cell debris (Skin lab, slide 23)