Developmental Biology Test #3 Set 2

Front 1

First body fold to appear

Back 1

head fold

tends to undercut and separate from the rest of the blastoderm

Front 2

Second set of folds to appear

Back 2

lateral folds (develop on either side of the body)

Undercut the body further separating it from the embryo

Front 3

Third fold to appear. When does it appear?

Back 3

Caudal fold (undercuts the tail)

Appears on the third day

Front 4

What is the embryo separated from the extraembryonic components by

Back 4

a body stalk

Front 5

What is the first extraembryonic membrane to appear? What does it grow over?

Back 5

Yolk sac appears first

Grows over the yolk surface

Front 6

What does the dorsal wall function as?

Back 6

Primitive gut

Front 7

What does the yolk act as

Back 7

A temporary floor

Front 8

What does the yolk sac eventually do?

Back 8

Forms a sac-like structure around the yolk

Front 9

What happens concomitantly with the yolk sac?

Back 9

A completely walled gut develops in the body of the embryo

Front 10

What happens to the yolk sac by the 19th day?

Back 10

the remains are enclosed within the body wall of the embryo

remaining yolk is absorbed within 6 days after hatching

Front 11

What does the amnion enclose?

Back 11

The embryo in a water-filled sac

Front 12

What do the muscle fibers in the amnion do?

Back 12

agitate the fluid

Front 13

What does the slow, rocking motion aid

Back 13

In keeping the parts of the embryo free from one another.

Front 14

Chorion

Back 14

- Eventually envelopes the yolk sac

- Transports Ca2+ from egg shell into embryonic circulation (used for development of the beak and skeleton)

Front 15

Allantois

Back 15

- Highly vascularized and is important in respiration

- 21 days prior to hatching, takes up 5 L of oxygen and gives off 4 L of carbon dioxide (other liter of carbon dioxide is incorporated into CaCO3

- Reservoir for the toxic products of protein metabolism (urea and uric acid)

Front 16

What does the embryo mainly excrete in the first part of development? Later part of development (what does this deal with)?

Back 16

- Urea

- Uric acid (helps deal with the build up of urea which is much more toxic)

Front 17

What does the allantois do at hatching?

Back 17

Remains attached to the broken shell

Front 18

Does a mammal form a yolk sac?

Back 18

Yes

Front 19

What does the amnion do in humans?

Back 19

Enfolds the developing embryo as in the chick

Front 20

What does the allantois contain at full term in humans?

Back 20

Almost a full liter of fluid

Front 21

What does the allantois develop as in a mammal?

Back 21

The diverticulum of the hindgut

Front 22

What does the chorion do after the completion of the amnion?

Back 22

Completely surrounds the complex of the embryo and its other membranes and serves as an interface between embryonic tissues and the uterus.

Front 23

Placenta

Back 23

- Region in the uterus where the interchange of food, gases, and wastes takes place between the fetus and its mother

- Consists of tissue contributed by both the embryo and the mother

- Large amount of surface area (10m2 or 3.16x3.16 m) due to villli

Front 24

How is the embryo linked to the placenta?

Back 24

By a stalk of tissue consisting of tissues from the body of the embryo, the allantois, and the yolk sac

Front 25

What happens as the circulatory system develops?

Back 25

The allantoic blood vessels carry blood, through the stalk, connecting the embryo and the capillary beds of the placenta

Front 26

What does the stalk develop into?

Back 26

The umbilical cord, with an umbilical artery and vein

Front 27

Where does the embryo normally implant itself?

Back 27

in the upper part of the uterine cavity

Front 28

How is the embryo nourished during the early phase of implantation?

Back 28

By diffusion

Front 29

Decidual Reaction

Back 29

The cells of the uterus enlarge and their cytoplasm becomes filled with glycogen and lipid droplets

Front 30

What do the cells of the decidual reaction do?

Back 30

- Help to maintain immunological compatibility between the embryo and the mother (appear to be derived from bone marrow)

- Cells are sloughed off after birth and shed postpartum

Front 31

Villi

Back 31

- Extensive system develops in the chorion

- Majority of the villi lie free in the blood spaces (lacunae) in the uterine layer

Front 32

How often is the placenta blood completely replaced? How much blood does it contain?

Back 32

- Every 3 minutes

- 150 mL of blood

Front 33

Is there ever any mixing of fetal and maternal blood?

Back 33

NO

Front 34

What are ways that food and wastes pass through the placental barrier?

Back 34

- Diffusion (by O2 and H2O)

- Active transport (by sugars and amino acids)

- Pinocytosis (by proteins and antibodies)

Front 35

What are the two placental protein hormones?

Back 35

1. Human chorionic gonadotropin (hCG)

2. Human placental lactogen

Front 36

Human chorionic gonadotropin (hCG)

Back 36

- Basis for many pregnancy tests

- Maintains the corpus luteum which in turn produces progesterone and estrogen

Front 37

Human placental lactogen

Back 37

Facilitates energy supply to the fetus

Front 38

Corpus luteum

Back 38

- the cells around the follicle develop into this after ovulation

- temporarily maintains the pregnancy until the placenta takes over

Front 39

Placental steroid hormones

Back 39

- Progesterone

- Estrogens

- Placenta eventually makes enough steroid hormones that the corpus luteum undergoes atresia

Front 40

What signals birth

Back 40

A peptide hormone produced by the brain of the fetus

Front 41

Why does the fetus remain attached to the placenta during birth?

Back 41

-Essential to get oxygen because the baby is not breathing at this time

Front 42

Why is the placenta eaten by some animals?

Back 42

- Source of hormones which stimulate lactation and maternal instincts

- Allows for chemical imprinting of the mother on the baby animal

- Reduces scent which might attract predators

- Conserves materials such as Ca2+