Lec 2: Skin and glands (ROTHWELL)

Question 1

Where can mitosis in the skin occur?

Answer 1

Up through the several layers of the epidermis to the top of the stratum spinosum.

Question 2

Where is keratin cross linked? (Inside or outside cells)

Answer 2

Inside cells to create the strength of the epidermis.

Question 3

What division of the nervous system and what neurotransmitter affect the sweat glands?

Answer 3

Sympathetic NS and it uses acetylcholine. (According to the image on the slides).

Question 4

List the 5 functions of the integumentary system.

Answer 4

1 - Protection (From physical insults and microorganisms via APCs)2- Thermoregulation (Sweat, fat layers, and arteriolar/capillary dilation and constriction)3- Metabolism (Vitamin D3 from UV exposure)4- Sensory (Nerves, duh)5- Sexual signaling (with regards to health/age)

Question 5

5 Layers of the epidermis? (Starting from the outside).

Answer 5

Stratum CorneumStratum Lucidum (in thick skin only)Stratum GranulosumStratum SpinosumStratum Basale

Question 6

How would you identify the stratum corneum?

Answer 6

Stacks of anucleated stratified squamous keratinized epithelial cells.

Question 7

How would you identify the stratum lucidum?

Answer 7

Very very thin clear layer of cells (non-staining) just under the stratum corneum.

Question 8

How would you identify the stratum Granulosum?

Answer 8

Lots of dark staining keratohyalin granules with lamellar bodies forming near the top of the layer.

Question 9

How would you identify the stratum spinosum?

Answer 9

Think of the name. Spinosum -> Spiny. You can see the desmosomes that hold the epithelial cells together here and they look like spines on the outside of the cell. In addition you can probably also spot some tonofilaments that are developing.

Question 10

How would you identify the stratum basale?

Answer 10

The last layer on the interior of the cell before the dermis (with the dermal papillae) start. Should also see plenty of mitosis and melanocytes at this level. Cells will be nearly cuboidal to columnar.

Question 11

What are the two layers of the dermis?

Answer 11

Papillary and reticular layers.

Question 12

What do you see in the hypodermis?

Answer 12

Subcutaneous adipose, hair follicles and even more adipose.

Question 13

What do you see in the Papillary layer of the dermis?

Answer 13

Areolar connective tissue, dermal papillae.

Question 14

What do you see in the Reticular layer of the dermis?

Answer 14

Dense irregular CT with hair follicles sebaceous and sweat glands as well as nerves.

Question 15

2 ways to recognize thick skin on slides?

Answer 15

Stratum lucidum will be present and there will be NO hair at all.

Question 16

How does the melanocyte lead to pigmentation of skin and hair?

Answer 16

It creates melanin, those become part of melanosomes and extend to be taken up by other cells. The melanin is then broken down. The speed at which it is broken down in the keratinocytes determines the extent of pigmentation.

Question 17

What are the APCs in the skin called?

Answer 17

Langerhan’s Cells. They sample in the epidermis and take any microbes to the lymphatic system for an immune reaction if it is warranted.

Question 18

How does the skin transmit information to the nervous system?

Answer 18

It has nerves all throughout and specialized receptors on the ends of nerves to sense different kinds of sensation.

Question 19

Epithelial tactile cells are AKA? Describe them.

Answer 19

Merkel Cells. Mechanoreceptors for light touch sensation. Joined together by desmosomes to keratinocytes of the basal epidermal layer. You’ll see a lot of them in sensitive skin areas like the fingertips. The basolateral surfaces of the cells contact expanded terminal disks of unmyelinated sensory fibers that penetrate the basal lamina.

Question 20

Describe how the vascular system participates in thermal regulation.

Answer 20

Arteries -> arterioles -> capillary beds. The capillaries have their flow controlled at the level of the arterioles and so when the arterioles dilate more blood flows in and the extra blood now has increased surface area closer to the outside where it can shed heat and cool the person off. When the arterioles constrict then the blood doesn’t reach the outside surface area of the body to shed its heat and the warmth is retained.

Question 21

Describe the layers of a hair and how they look on slides.

Answer 21

They’ll be big holes in the reticular layer of the dermis. The inner most portion is a core called the medulla. On the way out you get the cortex, cuticle, inner and outer root sheaths.

Question 22

Describe sweat glands on H&E slides.

Answer 22

Small clusters of darker/lighter staining circles. The darker cells secrete a more proteinaceous fluid and the lighter ones secrete a more watery portion of sweat. Some of the circles you’ll see are the ducts themselves that have myoepithelial cells around them to help in a sort of - reverse peristaltic action - to move sweat out of the gland.

Question 23

What are the three types of glands?

Answer 23

Exocrine, Endocrine and paracrine.

Question 24

What are the three types of exocrine glands?

Answer 24

Merocrine, apocrine and holocrine.

Question 25

Describe the process of merocrine secretion.

Answer 25

Granules of product are excreted into ducts.

Question 26

Describe the process of apocrine secretion.

Answer 26

Granules of product bud off with bits of cytoplasm into the ducts.

Question 27

Describe the process of holocrine secretion.

Answer 27

The gland itself becomes the product and turns itself into the product to enter into the duct.

Question 28

Describe the hierarchy of ducts and duct works…

Answer 28

Gland acini -> intercalated ducts -> Striated ducts.

Question 29

Describe the reflex arc.

Answer 29

Pain (or other sensation) is strong enough that as it travels up the sensory neuron in the dorsal portion of the spine it can jump over to the motor neuron in the anterior portion of the spine and cause it to fire to remove yourself from the source of the pain. Takes about .2 seconds, half of which is your muscles coordinating a proper pull back.

Question 30

Describe the embryonic origins of the epidermis.

Answer 30

At about 5 weeks there is a layer of ectoderm over a mesenchyme layer. Within another two weeks the “periderm” forms on top of it. The periderm gives rise to the start of the epidermis (the start of the stratum spinosum with the layer of ectoderm that it grew on now acting as the germinative layer). The layer of mesenchyme it sat on becomes the “corium”.

Question 31

Describe the embryonic origins of the dermis.

Answer 31

This is derived from the chorium under the epidermal germinative layer. About month 3 and 4 dermal papillae form and glands and hair follow. The dermis mesenchyme varies by source for each body area.

Question 32

BONUS: What are the sources of dermis for the three main areas?

Answer 32

1) Lateral plate mesoderm -> Dermis for limbs and the body wall
2) Paraxial mesoderm -> Dermis for the back
3) Neural crest cells -> Dermis for the face and neck.