Embryology Flashcards
Define the stages of embryology
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
Describe the formation of the gametes and fertilisation
Describe the formation of the blastocyst and its implantation into the uterine wall
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.
Outline the formation of the placenta, placental villi and the general functions of the
placenta
villi for vascularisation of the placenta.- give foetal brain nutrition
Describe the formation of the bilaminar disc
cells of inner mass flatten and form a 2 layered bilaminar disc and two cavities begin to form called amniotic cavity and yolk sac
Describe the formation of the trilaminar disc
function of blastocyst cavity
to get nutrients to the cell
what are the outer layer of the cells called
trophoblasts
what happens to the cells that form the outer cell mass known as trophoblast
divide to form 2 layers and forms a chorion which develops finger like processes called chorionic villi
function of chorion
involved in inplantation, forms part of the placenta in due course and secretes human chorionic gonadotropin
main functions of placenta
foetal nutrition, transport of waste and gases, immunity
gastrulation
formation of germ layers
neurulation
formation of neural tube
what is the primitive streak
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
describe gastrulation
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
describe neurulation
ectoderm cells sink down to form a solid tube called a notochord. Notochord induces ectodermal cells in the midline to form a neural tube
describe mesoderm
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
what does paraxial mesoderm form
somites and divides into 3- dermatome, myotome and sclerotome
what does each mesoderm form
paraxial forms somites
intermediate plate mesoderm forms kidneys and reproductive
lateral plate mesoderm forms body cavities and coverings
Briefly describe folding of the embryo and the formation of the gut tube.
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
describe the origin of the lung buds
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
Describe the development of the bronchial tree
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
Describe the development of the diaphragm
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
how does the gut tube form
folding of the somatic and sphanchinic mesoderm from the endoderm
development of pleura
splanchnic layer of lateral plate mesoderm forms visceral pleura
somatic layer of lateral plate mesoderm forms parental pleura.
what is fistula
an abnormal passed between 2 epithelialized tubes or surfaces
what is atresia
a condition in which a passage in the body is closed or absent
what is the pericardioperitoneal canal
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
what is the pericardioperitoneal canal
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
how do you seal the pericardoperitoneal canal
formation of pleuroperocaridal folds formed from the body wall and lined by somatic mesoderm. once this occurs it becomes known as the pleural cavity
formation of alveolar crest
by the secondary crests that protrude from the walls of the terminal sacs
where does trachea form from
foregut endoderm
splanchnic mesoderm develops into what structure
visceral pleura
when does gas exchange start to occur
saccular stage
parietal pleura develops from what
somatic mesoderm
