Development of the Integument

Question 1

When is the 3-layered epidermis formed and what are the three layers?

Answer 1

Formed by the end of the third month

Basal (germinative) layer
Intermediate layer
Superficial Peridermal layer

Question 2

What is the intermediate layer composed of?

Answer 2

Stratum spinosum

Stratum granulosum

Question 3

What are the 3 Immigrant cells? They are called immigrant cells because they migrate to the epidermis after it has been developed.

Answer 3

Melanoblasts
Langerhan’s cells
Merkel cells

Question 4

Describe Melanoblasts, where they are from, where they migrate to, and when they produce their product

Answer 4

From the neural crest

Migrate into the dermis and then into the epidermis

Produce pigment by mid-pregnancy

Question 5

Describe Langerhans cells, where they are derived from and their function

Answer 5

Derived from bone marrow

APC’s

Question 6

Describe Merkel cells, where they are derived from and their functions

Answer 6

From neural crest

Slow-adapting Mechanoreceptors

Question 7

What are the 3 aspects of the body that are the origin of dermal cells? Describe where the mesenchyme came from each

Answer 7

Dorsal surface of the body- Mesenchyme from dermatome

Ventral and lateral surfaces of the body - Mesenchyme from lateral plate mesoderm

Cranial and anterior neck- Mesenchyme from cranial neural crest

Question 8

What is it called when one germ layer instructs another on how to differentiate?

Answer 8

Instructive Induction

Question 9

What are the 3 epidermal derivatives?

Answer 9

Hair
Nails
Mammary glands

Question 10

Development of hair, nails, and mammary glands involves _______ and _________ interactions and inductions

Answer 10

Ectodermal

Mesodermal

Question 11

Hairs, nails, and mammary glands begin as _______ ______ into the mesenchyme

Answer 11

Epidermal downgrowths (ingrowths)

Question 12

______ contributes to the hair follicle, hair shaft, sebaceous glands, nails, eponchium, hyponychium, and secretory and duct components of the mammary glands

Answer 12

Ectoderm

Question 13

_____ contributes to the hair papilla, outer hair follicle, and arrector muscles

Answer 13

Mesenchyme

Question 14

Describe how recombination experiments (3 of them) between the mesoderm (source of the dermis) and the ectoderm (source of the epidermis) demonstrate instructive induction.

Answer 14

1. If the ectoderm is alone, it does not differentiate into the epidermis. If the Mesenchyme is alone, it does not differentiate into the dermis.
2. Abdominal ectoderm with Sole mesoderm underneath it –> Thickened Sole ectoderm
3. Sole ectoderm with Scalp mesoderm –> Scalp skin with hair
   * 2 and 3. If the Ectoderm and the underlying mesenchyme are expressed together, the dermis determines the nature of the ectodermal differentiation- Instructive Induction

Question 15

What stimulates the production of milk in breastfeeding?

Answer 15

Prolactin release from the hypothalamus

Question 16

What stimulates the nervous system to allow for the release of prolactin and let milk flow during breastfeeding?

Answer 16

Oxytocin