Embryology

Question 1

Define the stages of embryology

Answer 1

zygote is formed and divides to form a blastocyst. moves through uterine tube to reach uterine cavity. implantation occurs in the uterine endometrial layer and placenta begins to develop

Question 2

Describe the formation of the gametes and fertilisation

Question 3

Describe the formation of the blastocyst and its implantation into the uterine wall

Answer 3

During fertilization, the sperm and egg unite in one of the fallopian tubes to form a zygote. Then the zygote travels down the fallopian tube, where it becomes a morula. Once it reaches the uterus, the morula becomes a blastocyst. The blastocyst then burrows into the uterine lining — a process called implantation.

Question 4

Outline the formation of the placenta, placental villi and the general functions of the
placenta

Answer 4

villi for vascularisation of the placenta.- give foetal brain nutrition

Question 5

Describe the formation of the bilaminar disc

Answer 5

cells of inner mass flatten and form a 2 layered bilaminar disc and two cavities begin to form called amniotic cavity and yolk sac

Question 6

Describe the formation of the trilaminar disc

Question 7

function of blastocyst cavity

Answer 7

to get nutrients to the cell

Question 8

what are the outer layer of the cells called

Answer 8

trophoblasts

Question 9

what happens to the cells that form the outer cell mass known as trophoblast

Answer 9

divide to form 2 layers and forms a chorion which develops finger like processes called chorionic villi

Question 10

function of chorion

Answer 10

involved in inplantation, forms part of the placenta in due course and secretes human chorionic gonadotropin

Question 11

main functions of placenta

Answer 11

foetal nutrition, transport of waste and gases, immunity

Question 12

gastrulation

Answer 12

formation of germ layers

Question 13

neurulation

Answer 13

formation of neural tube

Question 14

what is the primitive streak

Answer 14

formed in the midline of the epiblast by the dipping in of cells (invagination). Once primitive streak forms the axis of the embryo is formed

Question 15

describe gastrulation

Answer 15

epiblasts cells migrate to lie in-between epiblast and hypoblast layers. cells displace hypoblast layers and forms 3 germ layers
1. ectoderm
2. mesoderm
3. endoderm
trilaminar disc is now formed

Question 16

describe neurulation

Answer 16

ectoderm cells sink down to form a solid tube called a notochord. Notochord induces ectodermal cells in the midline to form a neural tube

Question 17

describe mesoderm

Answer 17

neural tube causes mesoderm to thicken and spilt into 3 parts called
paraxial mesoderm, intermediate plate mesoderm and lateral plate mesoderm and lateral plate splits again

Question 18

what does paraxial mesoderm form

Answer 18

somites and divides into 3- dermatome, myotome and sclerotome

Question 19

what does each mesoderm form

Answer 19

paraxial forms somites
intermediate plate mesoderm forms kidneys and reproductive
lateral plate mesoderm forms body cavities and coverings

Question 20

Briefly describe folding of the embryo and the formation of the gut tube.

Answer 20

during folding the somatic (parietal) mesoderm folds down to surround the splanchnic (visceral) mesoderm if the intraembryonic body cavity. The yolk sac becomes absorbed into the primitive gut

Question 21

describe the origin of the lung buds

Answer 21

trachea and lungs bud out from the ventral/anterior wall of the primitive foregut. closely surrounded by lateral plate splanchnic mesoderm. a septum develops between oesophagus and trachea to separate them and lung buds will enlarge to from the lungs

Question 22

Describe the development of the bronchial tree

Answer 22

tracheal epithelium and glands are derived from endoderm
tracheal smooth muscle, connective tissue, and cartilage are derived from visceral (or splanchnic) mesoderm. At week 4 trachea splits into two bronchi

Question 23

Describe the development of the diaphragm

Answer 23

Septum transverse forms the central tendon

Somatic mesodermal folds from in from the peripheral wall to fuse with sputum transverse. They close off pleuroperitoneal canals and stop abdominal contents getting into thorax

skeletal muscle grows inwards from the peripheral body wall forming muscular part of diaphragm

Dorsal mesentery of the oesophagus attaches to the posterior thoracic wall and skeletal muscle covers the dorsal mesentery to from the diaphragmatic crura

Question 24

how does the gut tube form

Answer 24

folding of the somatic and sphanchinic mesoderm from the endoderm

Question 25

development of pleura

Answer 25

splanchnic layer of lateral plate mesoderm forms visceral pleura
somatic layer of lateral plate mesoderm forms parental pleura.

Question 26

what is fistula

Answer 26

an abnormal passed between 2 epithelialized tubes or surfaces

Question 27

what is atresia

Answer 27

a condition in which a passage in the body is closed or absent

Question 28

what is the pericardioperitoneal canal

Answer 28

space between the splanchnic and somatic mesoderm around the lungs that is initially continuous with the pericardial and peritoneal cavity. the cavity needs to be sealed off to maintain pleural cavity pressure

Question 28

what is the pericardioperitoneal canal

Answer 28

space between the splanchnic and somatic mesoderm around the lungs that is initially continuous with the pericardial and peritoneal cavity. the cavity needs to be sealed off to maintain pleural cavity pressure

Question 29

how do you seal the pericardoperitoneal canal

Answer 29

formation of pleuroperocaridal folds formed from the body wall and lined by somatic mesoderm. once this occurs it becomes known as the pleural cavity

Question 30

formation of alveolar crest

Answer 30

by the secondary crests that protrude from the walls of the terminal sacs

Question 31

where does trachea form from

Answer 31

foregut endoderm

Question 32

splanchnic mesoderm develops into what structure

Answer 32

visceral pleura

Question 33

when does gas exchange start to occur

Answer 33

saccular stage

Question 34

parietal pleura develops from what

Answer 34

somatic mesoderm