Histology Integument Aug 25 2014 (Lecture 1)

Question 1

What are the layers of skin?

Answer 1

Epidermis

Question 2

What are the 5 layers of the Epidermis?

Answer 2

From top layer to the bottom.

C L G S B

◦ stratum corneum

◦ stratum lucidum

◦ statum granulosum

◦ stratum spinosum

◦ stratum basale (germinativum)

Question 3

What are the 2 layers of the dermal papillae?

Question 4

What is the difference between thick and thin skin?

Answer 4

◦ thick skin: epidermis is around 5 mm thick

Question 5

What do the Keratinocytes in the stratum basale look like?

Question 6

What do the Keratinocytes in the stratum spinosum look like?

Question 7

What do the Keratinocytes in the stratum granulosum look like?

Question 8

What do the Keratinocytes in the stratum lucidum look like?

Question 9

What do the Keratinocytes in the stratum corneum look like?

Question 10

What are melanocytes?

Answer 10

◦ specialized cells found in the stratum basale
◦ originate as neural crest cells
◦ melanocytes produce melanin (melanosomes) which are transferred to keratinocytes
◦ MITF (microphthalemia-associated transcription factor

Question 11

What are Langerhans cells?

Answer 11

◦ dendritic cells (derived from bone
marrow) located in stratum
spinosum
◦ clear cytoplasm, irregularly
shaped nucleus, Birbeck granules
◦ involved in immune responses
◦ antigen-presenting cells
◦ monitor foreign antigens that
contact epidermis
◦ phagocytic cells that leave the
epidermis, enter the lymphatic
system; travel to lymph nodes and
there interact with T cells
◦ activated T cells then travel back
to the epidermis through the
blood stream and release proinflammatory
cytokines to
neutralize the antigen

Question 12

What are Merkel cells?

Answer 12

◦ resemble keratinocytes
◦ develop from neural crest
◦ found in stratum basale of
specialized areas of the
body such as fingertips
and are associated with the
basal lamina
◦ mechanoreceptors
connected to a myelinated
nerve fiber in the dermis
◦ irregularly shaped nucleus
with granular cytoplasm

Question 13

What are the steps in wound healing?

Answer 13

1. formation of a fibrin-platelet clot ◦ platelets are embedded in a fibrous mesh of fibrin ◦ thrombin cleaves fibrinogen to form fibrin ◦ platelets release platelet-derived growth factor
2. Leukocyte recruitment ◦ keratinocytes and endothelial cells express CXC and CXC receptor which recruit neutrophils, monocytes and lymphocytes ◦ monocytes become macrophages ◦ neutrophils release pro-inflammatory cytokines and activate fibroblasts and keratinocytes
3. Neovascularization and cellular proliferation ◦ new blood vessels form and organize granulation tissue
4. Tissue remodeling ◦ keratinocytes from the stratum basale migrate from the edges of the wound ◦ hemidesmosomes detach and allow movement ◦ matrix metalloproteinases are produced by fibroblasts ◦ epidermal growth factors facilitate re-epithelialization ◦ underlying dermis contracts to bring edges of the wound together ◦ fibroblasts infiltrate and produce Type III collagen

Question 14

What is Psoriasis?

Answer 14

Psoriasis is an inflammatory skin disorder

◦ initiated by Langerhans
cells

Question 15

What are the of sensory receptors by stimulus?

Answer 15

◦ mechanoreceptors

Question 16

What are the 3 types of glandular secretions?

Answer 16

Merocrine
◦ releases secretory product by
exocytosis

Holocrine
◦ the entire cell
becomes the
secretion

Apocrine
◦ releases a
portion of the
cell cytoplasm
with secretion

Question 17

What are Sebaceous glands?

Answer 17

◦ are associated with
hair follicles or
empty directly
onto the skin

◦ produce sebum
which is a lipid rich
substance that
is oily

◦ holocrine secretion

Question 18

What are the 2 types of sweat glands?