embryology

Question 1

what are the testis tubules called?

Answer 1

seminiferous tubules

Question 2

what are the cells in the seminiferous tubules called?

Answer 2

spermato gonia

Question 3

what do the follicles in the ovary contain?

Answer 3

oogonia, which divide to form an ovum

Question 4

how many chromosomes do gametes (sperm and ovum) have combined?

Answer 4

46
44 autosomes (not sex)
1 pair of sex chromosomes
xy in male, xx in female

Question 5

what is a morula?

Answer 5

a solid ball of cells

Question 6

what 2 lots does morula divide into?

Answer 6

trophoblast - the outer lining of cells
blastocyst - inner cell mass

Question 7

what structure helps the blastocyte travel to the uterine cavity?

Answer 7

ciliated epithelium

Question 8

what is an ectopic pregnancy?

Answer 8

damaged ciliated epithelium prevents the zygote from moving down the uterine tube leading to implantation outside the uterine cavity

Question 9

what does the trophoblast form?

Answer 9

2 layers, forming chorion

Question 10

what are the chorion finger-like processes called?

Answer 10

chorionic villi

Question 11

what are the 3 functions of chorionic villi?

Answer 11

• helps the implantation process
• forms part of the placenta
• secretes human chorionic gonadotropin (HCG)
  –> used to detect pregnancy

Question 12

what is the uterine wall (endometrium) called after implantation?

Answer 12

decidua basalis

Question 13

what are the 3 functions of the placenta?

Answer 13

foetal nutrition

transport of waste and gas

immune system

Question 14

during the second week, the blastocyst flattens itself into what 2 layers?

Answer 14

epiblast - top layer

hypoblast - bottom layer

Question 15

what divides the blastocyst cavity?

Answer 15

2 layer flat disc/ bilaminar disc

Question 16

what 2 cavities are formed from the blastocyst cavity?

Answer 16

amniotic cavity - top layer

yolk sac - bottom layer

Question 17

what is the primitive streak that’s formed in the 3rd week? what is its function?

Answer 17

formed in midline of epiblast by dipping of cells

gives embryo axis - helps to identify if anterior, posterior etc.

Question 18

Why do epiblast cells sink from epiblast?

Answer 18

to form a new layer between epiblast and hypoblast

Question 19

what are the three germ layers (gastrulation) formed from cells replacing hypoblast? In descending order

Answer 19

ectoderm

mesoderm

endoderm

Question 20

How is the notochord formed? What is the function of the notochord?

Answer 20

cells from primitive streak sink to form notochord which sits between the meso and endoderm

notochord induces ectodermal cells in the midline to form a neural tube

Question 21

describe neurulation(neural tube formation)

Answer 21

Thickening of the neural plate in ectoderm sinks down

2 neural crests come together to form a neural tube, which gets disconnected from the ectoderm

forms the brain and spinal cord

Question 22

what 3 parts is the mesoderm split into?

Answer 22

• paraxial mesoderm
• intermediate plate mesoderm
• lateral plate mesoderm

Question 23

what 2 arms does a lateral plate mesodermal split into?

Answer 23

Somatic mesoderm

splanchnic mesoderm

Question 24

What is the cavity between the somatic and splanchnic mesoderm called?

Answer 24

intraembryonic coelom/ cavity

Question 25

what are somites formed from?

Answer 25

paraxial mesoderm

Question 26

how many somites are there?

Answer 26

44 initially 35-37 Finally

Question 27

What three structures does each somite divide into?

Answer 27

dermatome myotome sclerotome

Question 28

where does dermatome migrate to and form?

Answer 28

migrates to underneath ectoderm - dermis of skin

Question 29

where does myotome migrate to and form?

Answer 29

different regions - muscles

Question 30

where does sclerotome migrate to and form?

Answer 30

neural tube - bones

Question 31

in weeks 4-8, what does the neural tube form?

Answer 31

forebrain, midbrain, hindbrain and spinal cord

Question 32

define teratology and teratogens:

Answer 32

Teratology - the study of when things go wrong during development Teratogens - environmental factors that cause abnormal development

Question 33

list some teratogens:

Answer 33

alcohol & smoking drugs pathogens radiation

Question 34

what weeks embryo development has the least and greatest sensitivity to teratogens?

Answer 34

Weeks 1-2 of pre-embryonic phase: high risk of death (abortion), so less risk of a fetus born with teratogens. Weeks 3-8 of embryo development: the periods of greatest sensitivity to teratogens. Weeks 9-38 of embryo development: have decreasing sensitivity to teratogens.

Question 35

what 3 factors does risk posed by a teratogen depend on?

Answer 35

Exposure during critical periods of development Dosage of drug/chemical/factor Genetic constitution of embryo

Question 36

state 3 prenatal diagnosis of malformations:

Answer 36

Maternal Blood - Alpha Feto Protein Ultrasound scan – 12 week anomaly scan - Invasive tests: chorionic villus sampling and amniocentesis