Embryonic Disk and more

Question 1

label the parts of the embryonic disk

Answer 1

drawn out

Question 2

what is the amniotic cavity

Answer 2

forms the inside inner cell mass and surrounded by layer of cells called the amnion or amniotic sac

Question 3

what structures form after implantation

Answer 3

embryonic disk
composed of 2 layers - epiblast and hypoblast
- the amniotic cavity eventually covers the developing embryo providing a protective fluid bag

yolk sac
forms inside blastocele from hypoblast

Question 4

what is the epiblast

Answer 4

its 3 germ layers that becomes the embryo

Question 5

what is the hypoblast

Answer 5

its extraembryonic memebrane and helps with extra embryonic tissue

Question 6

explain what happens during day 13-14 (gastrulation) - formation of germ layers

Answer 6

• cephalic end = Becomes head
• caudal end = Becomes base of torso
• epiblast layer multiplies and thickens along primitive streak

These 3 germ layers are gonna form all of the body tissues:
- Ectoderm –> skin and most of nervous system
- Mesoderm –> blood supply, bones and muscles
- Endoderm –> digestive system, lungs

Question 7

describe the formation of the germ layers

Answer 7

endoderm
- Inner layer
- forms lining of digestive tract and derivatives

mesoderm:
- middle layer
- forms tissues like muscle, bone. blood vessels

ectoderm:
- outer layer
- forms skin and nervous system

Question 8

what happens at day 16 - formation of notochord

Answer 8

• mesodermal cells are formed
• solid cylinder of cells under the ectoderm –> becomes neural plate at day 18
• notochord is involved in induction of signals from ectoderm to the neural plate and it at the cephalic end (the primitive streak is at caudal end)

Question 9

what does the oropharngeal membrane becomes?

Answer 9

mouth

Question 10

what does the cloacal membrane becomes?

Answer 10

anus - end of digestive system

Question 11

what happens on day 18-26 - formation of neural tube

Answer 11

• Notochord has sent a signal to ectoderm –> thickens it and becomes neural plate
  neural plate Forms neural folds and a central indentation called a neural groove
  -
  Neural folds becomes higher and neural indentations get bigger
• Ridges = crest of neural fold
• Crests come together and form an outer layer (becomes skin) at the top and it makes a tube in the middle (neural tube that becomes spinal cord and brain)
• Outside neural tube theres somites thats formed from mesoderm

Question 12

what does the neural tube form

Answer 12

forms the brain and spinal cord (CNS)

Question 13

what does the neural crest form?

Answer 13

• sensory and post ganglionic autonomic (cant consciously control) portions of PNS
• general CT of the head

Question 14

what is a somite formed from and what does it become?

Answer 14

formed from mesoderm adjacent to neural tube

eventually become vertebral column, ribs, and some skeletal muscle

Question 15

what is the importance of the neural plate and how is it formed?

Answer 15

it becomes the spinal cord and brain

the notochord sends signals from the mesoderm to the ectoderm layer to thicken ectoderm and become neural plate

Question 16

what are the two types of embryonic folds? explain.

Answer 16

1. lateral body fold
   - across the length of the neural tube
2. fold in the median plane
   - this forms the ends called the hindgut and foregut

Question 17

what does the lateral fold produce?

Answer 17

• it forms the gut tube from the endoderm
• coelom within the mesoderm –> body cavities
• ectoderm –> skin

Question 18

what does the median plane fold produce?

Answer 18

• foregut and hindgut
• allantois

Question 19

What is the allantois?

Answer 19

a region of the yolk sac that is pinched off and ends up in the connecting stalk and becomes a part of the urinary system.

Question 20

what happens at day 20 of embryo folding and gut formation?

Answer 20

the amniotic cavity folds around the 3 germ layers into 2 different ways

• longitudinally - forms gut tube
• medially - forms head and tail

Question 21

what happens at day 25 of embryo folding and gut formation?

Answer 21

• the folds get closer to each other and the midgut is now defined.
• oropharyngeal is in contact with endoderm = mouth opening
• cloacal membrane and region under disappear = anus
• yolk sac is narrowed and celom gets longer

Question 22

what happens at day 30 of embryo folding and gut formation?

Answer 22

lateral folds fuse to form:
- amniotic cavity is around all germ layers like the whole embryo
- gut tube from oropharyngeal to cloacal membrane

evaginations from gut tube form:
- anterior pituitary, thyroid gland, lungs, liver, pancreas
- branchial arches

coelom:
- fuses around the heart as pericardial cavity
- expands to become the pleural and peritoneal cavities
- cavities become separate entities.

Question 23

what is evagnation

Answer 23

turning the gut tube inside out?

Question 24

what is the coelom?

Answer 24

A fluid-filled cavity lined by mesoderm tissue.

Question 25

what do brachial arches form?

Answer 25

pharynx, auditory tubes, tonsils, thymus and parathyroid glands

Question 26

when does limb bud development occur?

Answer 26

upper limb = day 24
lower limb = day 28

Question 27

what is limb bud development?

Answer 27

• limbs grow from proximal to distal
• mesoderm cells are proliferating

Question 28

what is the apical ectodermal ridge?

Answer 28

thickened ectoderm at distal end of each developing limb that stimulates outward growth

Question 29

what is the protein for limb bud development called?

Answer 29

sonic hedgehog

Question 30

what did taking thalidomide cause problems in children?

Answer 30

def: thalidomide = drug given to prego women to reduce sickness

caused:
because it inhibits the formation of blood vessels. if the apical ectodermal ridge doesnt have enough blood supply to grow it wont and the limb will be stunted

Question 31

where is the skeleton derived from?

Answer 31

mesoderm or neural crest cells

Question 32

where are muscles derived from?

Answer 32

myoblasts - derived from the somites that develop into skeletal muscle fibers

Question 33

where is the nervous system derived from?

Answer 33

neural tube and neural crest cells

Question 34

what is the foregut

Answer 34

oral cavity

Question 35

what is the hindgut

Answer 35

anus

Question 36

what is the midgut

Answer 36

mid duodenum