Exam 1 9/27 Davenport

Question 1

Week 4 to 8 of development is known as:

Answer 1

Organogenic period

Question 2

_____ constitutes most of the embryonic period

Answer 2

Organogenic period

Question 3

What happens during the organogenic period?

Answer 3

1. all major internal and external structures are established
2. Main organ systems have begun to develop - CV is the only one with more function
3. shape of embryo changes and has distinctly human appearance by 8th week

Question 4

When do you start to hear the fetal heartbeat?

Answer 4

Week 4-6

Question 5

During organogenic period, tissues and organs are differentiating rapidly so exposure to teratogens can cause?

Answer 5

major congenital anomalies

Question 6

What is the fate of the primitive knot and primitive streak?

Answer 6

Nothing; we don’t know where the underlying hypoblast cells go

Question 7

What remnants of the notochord do we see?

Answer 7

Nucleus pulposis between the intervertebral discs

Question 8

Between days 26-32, what starts to appear in the embryo?

Answer 8

Somites

Question 9

How many pairs of somites develop?

Answer 9

38-39

Question 10

Where do the somites appear?

Answer 10

Occipital region

Question 11

What happens to the mesoderm around the notochord?

Answer 11

Divides into paraxial mesoderm, intermediate, and lateral plate mesoderm

Question 12

Which mesoderm is continuous with the extraembryonic mesoderm?

Answer 12

Lateral plate mesoderm

Question 13

What tissue is responsible for the formation of somites?

Answer 13

paraxial mesoderm

Question 14

____ gives rise to spinal ganglia, which contributes to _____

Answer 14

neural crest cells; dermatomes
(nerves that come from the spinal ganglia will innervate the structures of those somites; as those somites grow they will form the dermatomes)

Question 15

True or false: dermatomes and nerves cross the midline

Answer 15

False

Question 16

Fate of somites

Answer 16

most of axial skeleton and associated muscles, UG system (kidneys and gonads)

Question 17

Fate of intermediate mesoderm

Answer 17

UG system

Question 18

Fate of lateral plate mesoderm

Answer 18

heart and CV system; blood; portions of the kidneys, smooth muscle, skeleton of the limbs

Question 19

Fate of ectoderm

Answer 19

1. epidermis
2. CNS and PNS
3. eyes
4. internal ear
5. neural crest
6. CT of head and neck

Question 20

Fate of mesoderm

Answer 20

1. all skeletal muscles
2. blood cells
3. lining of blood vessels
4. all visceral smooth muscle
5. lining of all body cavities
6. ducts and organs of the reproductive and excretory systems
7. most of CV system

Question 21

Exceptions to fate of mesoderm - what is derived from neural crest?

Answer 21

CT, cartilage, bones, tendons, ligaments, dermis, stroma of organs of the head

Question 22

Fate of embryonic endoderm

Answer 22

1. epithelium of the respiratory system and digestive system
2. ducts of glands
3. glandular cells of the liver and pancreas

Question 23

Teratogens can act between which weeks?

Answer 23

weeks 3-16 (highly sensitive period)

Question 24

What folds occur when embryo folds?

Answer 24

1 head fold, 2 lateral folds, 1 tail fold

Question 25

Folding of embryo causes:

Answer 25

1. trilaminar embryo changes into cylindrical tube
2. change in symmetry from mid axial to bilateral

Question 26

Folding is a result of differential growth because:

Answer 26

disc cannot keep up with growth in length as a result of developing nervous system

Question 27

What happens to the yolk sac as the embryo folds?

Answer 27

some is incorporated into embryo (foregut, midgut, hindgut –> GI tract)

Question 28

Direction of movement during embryo folding

Answer 28

Dorsal to ventral

Question 29

What eventually happens to the prechordal and cloacal plate?

Answer 29

They rupture so as to form a continuous tube in the embryo

Question 30

Some of the yolk sac stays ____ outside of the embryo - what is the significance?

Answer 30

herniated; gut is forming and rotates around the superior mesenteric artery, allows 32 ft of intestine to form in relation to SMA

Question 31

Why is the head fold important?

Answer 31

Puts everything where they need to be

Question 32

When the heart gets into place, we see the formation of:

Answer 32

2 dorsal aorta (branch of this supplies the pharyngeal arches)

Question 33

Stomodeum

Answer 33

primitive oral cavity

Question 34

How is embryonic age estimated?

Answer 34

determined from external characteristics and length measurements

Question 35

Methods of measuring embryonic age

Answer 35

1. during week 3-4, measuring GL (greatest length)
2. sitting height (crown-rump length) for older embryos
3. standing height or crown heel length - week 8