Lecture 25: Integument 1

Question 1

List the epithelial layers of thick skin in the correct order:

Answer 1

Stratum basale (germinativum)-deepest
Stratum spinosum
Stratum granulosum
Stratum lucidum 
Stratum corneum -superficial

Question 2

Discriminate btw the 2 layers of the dermis and list characteristics of each layer.

Answer 2

Papillary layer: loose CT, separated from epidermis by basal lamina. Network of fine elastic fibers and abundant capillaries.

Reticular layer: dense irregular CT. Includes fibrocytes, macrophages, and adipocytes.

Question 3

List characteristics of the hypodermis

Answer 3

Loose CT underlying dermis.
Corresponds to superficial fascia of gross anatomy.
Technically not part of the skin.
May contain fat cells that can form a thick layer called panniculus adiposus.

Question 4

Identify each layer of thick skin epidermis and dermis from photomicrographs.

Answer 4

Stratum lucidum is only in THICK skin

Dermis: papillary and reticular layer

Question 5

Compare thick skin to thin skin.

Answer 5

Thick skin: occurs on palms. ALL 5 layers.

Thin: rest of body. Thinnest on eyelids. Thickest is on back. Thinner on flexor than extensors. LACKING STRATUM LUCIDUM

Question 6

Explain how ridges are created in the skin to form the basis for fingerprinting.

Answer 6

Primary dermal ridge: r/t fingerprinting. Formed 3rd to 4th mon of life. Subdivided into 2 secondary dermal ridges by interpapillary peg (downward growth of epidermis along crest)

Secondary occurs in double rows and branched.

Question 7

Describe the process of keratinization

Answer 7

Simple cuboidal nucleated cells that begin to divide and lose nuclei. Leaving only keratin in cell.

Question 8

List the characteristics and functions of langerhans cells, merkel cells, and melanocytes.

Answer 8

Langerhans cells= dendritic cells 
From monocytes, 
Antigen-presenting cells,
Primarily in stratum spinosum, 
Migrate from epidermis to lymph nodes,
Birbeck granules 

Meckel’s cells= mechanoreceptors, may also act as diffuse neuroendocrine cells, usually in stratum germinativum, contain catecholamine-like granules

Melanocytes: from melanoblasts, dont form desmosome attachments in epidermis, inject melanin granules into keratinocytes.

Question 9

list major characteristics of each layer of epidermis:

Answer 9

Stratum basale (germinativum): columnar high cuboidal keratinocytes. Keratin 5 and 14. Single layer of cells. High mitotic activty.

Stratum spinosum: polyhedral shaped cells (prickle). Keratins 1 and 10. Keratohyalin granules develop. Membrane-coating granules 1st appear. Tonofibrils.

Stratum granulosum: multilayered. Keratins 2e and 9. Flattened nucleated keratinocytes. Keratohyalin aggregates, lamellar bodies. Tonofilaments.

Stratum lucidum: flat keratinocytes w/o nuclei/organelles. Only in thick skin. Contains eleiden

Stratum corneum: multilayer, thicker in thick skin, enucleated, flattened, dead keratinocytes. Cytoplasm replaced w/ keratin.

Question 10

Explain the embryonic origins of the epidermis and dermis.

Answer 10

Epidermis starts as a single layer of ectodermal.- divide during the 6th week to form.

Dermis is derived from mesoderm.