Chapter 3: Embryology

Question 1

Define teratogen.

Answer 1

A substance that can cause birth defects or death of the embryo.

ie. alcohol, tobacco smoke, drugs, some viruses, aspirin, etc

Question 2

Describe the germ layer: Ectoderm.

What body parts are derived from the ectoderm?

Answer 2

Epidermis of skin (including hair, nails, sweat glands, mammary glands)
Nervous tissue and sense organs
Pituitary gland 
Adrenal medulla
Enamel of teeth
Lens of the eye

Question 3

Describe the germ layer: Mesoderm.

What body parts are derived from the mesoderm?

Answer 3

Dermis of skin
Epithelial lining blood vessels, lymph vessels, serous membranes
Muscle tissue
Connective tissue
Adrenal cortex
Heart
Kidneys and ureters
Internal reproductive organs
Spleen

Question 4

Describe the germ layer: Endoderm.

What body parts are derived from the endoderm?

Answer 4

Epithelial lining of respiratory tract, GI tract, urinary tract, reproductive tract, tympanic cavity, auditory tube 
Lover
Gallbladder
Pancreas
Palatine tonsils
Thyroid gland
Parathyroid glands
Thymus

Question 5

What is meiosis?

Answer 5

A type of sex cell division that starts with a diploid parent cell and produces 2 haploid daughter cells

Question 6

What is mitosis?

Answer 6

Cell division process that takes place in the somatic cells (all cells of the body except the sex cells)
Results in 2 cells identical to the parent cell

Question 7

Define embryology.

Answer 7

The study of the developmental events that occur during the prenatal period.

Question 8

Define differentiation.

Answer 8

Formation and organization of all the cells in the human body.

Question 9

Define reproduction.

Answer 9

new individuals are produced from generation to generation.

Question 10

Define embryogenesis.

Answer 10

The developmental processes that occur in the pre-embryonic and embryonic periods.

Question 11

Define and describe gametogenesis.

Answer 11

Formation and development of sex cells (gametes).

Gametes (sperm in men; secondary oocytes in women) are each haploid (contain 23 chromosomes).

Question 12

List the developmental stages and structures in the pre-embryonic period.

Answer 12

First 2 weeks of development; zygote becomes a spherical, multicellular structure; blastocyst implants in the lining of uterus

zygote - 2 cell - 4 cell - morula - blastocyst

Question 13

Describe fertilization.

Answer 13

Two cells fuse to form a new cell called a zygote which contains genetic material derived from both parents.

Question 14

Name the 3 primary germ layers.

Diagram - Pg. 73

Answer 14

Ectoderm
Mesoderm
Endoderm

Question 15

Define the time period of the fetal stage of development.

Answer 15

The last 30 weeks of development.

Question 16

Define and describe spermatogenesis.

Answer 16

In males. Spermatogonia produce spermatocytes in the testes. They undergo meiosis and become spermatids who then lose much of their cytoplasm and grow a flagellum - becoming a sperm. 4 sperm come from 1 spermatocyte.
22 autosomes and 1 X or Y chromosome

Question 17

Define and describe oogenesis.

Answer 17

In females. Oocytes are produced by oogonia in the ovaries and they stop development in Prophase 1. Now they are a primary oocyte. When female reaches puberty, each month one becomes a secondary oocyte and is ovulated. The corona radiate and zone pellucid form protective layers around the secondary oocyte.
If not fertilized, it degenerates after 24 hours.
22 autosomes and 1 X chromosome.

Question 18

List and describe the 3 stages of embryogenesis.

Diagram - Pg. 55

Answer 18

Cleavage: zygote divides by mitosis to form blastocyst. # of cells incases but the whole size stays the same. After 3rd cleavage division cells become tightly compacted ball called a morula

Gastrulation: blastocyst cells form 3 primary germ layers

Organogenesis: the 3 primary germ layers arrange themselves in ways that give rise to all the organs within the body

Question 19

Amnion

Answer 19

thin layer of cells that forms above and is derived from the epiblast
encloses the entire embryo in a fluid filled sac called the amniotic cavity.
Amniotic membrane secretes fluid that bathes the embryo.

Question 20

Placenta

Answer 20

Functions in exchange of nutrients, waste, and respiratory gases between the maternal and fetal bloodstreams.
Transmission of antibodies from mom to baby.
Production of hormones to build and maintain the uterine lining.

Question 21

Outline structures and phases in meiosis.

Diagram - Pg. 57

Answer 21

Starts with diploid cell
Meiosis I produces 2 diploid daughter cells
Meiousis II turns 2 diploid cells into 4 haploid cells
Crossing over only occurs in prophase I

Question 22

Chorion

Answer 22

outermost membrane covering the fetus

cells blend with the functional layer of the endometrium and form the placenta.

Question 23

Gastrulation

Answer 23

3rd week of development.
Critical period in the development of the embryo
Formation of the 3 primary germ layers occurs:
Ectoderm, Mesoderm, Endoderm.

Question 24

Organogenesis

Answer 24

once 3 primary germ layers have formed, this can begin. Organ systems can develop and the shape of the limbs takes place.

Question 25

Discuss what happens in Meiosis.

Answer 25

1. Prophase: Maternal and paternal chromosomes pair and form tetrad; crossing over occurs between chromosomes ensuring genetic diversity.
2. Metaphase: chromosomes line up at the equator forming a double line of chromosomes; spindle fibers attach to centromeres
3. Anaphase: Chromosomes are pulled to the opposite ends of cell - reduction division
4. Telophase: nuclear division finishes and nuclear envelopes re-form; cytoplasm divides and the two new cells are produced.

Question 26

What stage of development does the secondary oocyte enter an arrested state?

Answer 26

Metaphase II

Question 27

Production of sperm and oocytes is achieved though what type of cell division?

Answer 27

Meiosis