Embryology and congential malformations

Question 1

Why study human embryology?

Answer 1

History of our prenatal origin
Understanding birth defects or congenital abnormalities
Understanding adult anatomy
Understanding basis for assisted reproductive technology

Question 2

Describe the embryological periods

Answer 2

Prenatal
-Embryonic(0-8 weeks)
-Fetal(8-38 weeks)
Postnatal (Infancy)

Question 3

What is gametogenesis?

Answer 3

The production of male and female gametes from primordial germ cells via meiotic cell division in the gonads

Question 4

What is a stem cell?

Describe the term: pluripotent, multipotent and totipotent.

Answer 4

An undifferentiated cell that has the ability to form specialised cell types.
Pluripotent - Can form all mature cell types in the body except placental and extraembryonic cells. It cannot form a whole organism.
Multipotent - Can form more than one closely related cell types in the body, but not as varied as pluripotent cells.
Totipotent - Can form all differentiated cell types in the body. These include the zygote and first few generations of blastomeres. Can form a whole organism

Question 5

What is fertilisation? Where does it occur?

Answer 5

Male and female gametes fuse to form a zygote. This occurs at the ampullary region of the uterine tube.

Question 6

How can infertility be treated?

Answer 6

Assistive reproductive technology (ART)

Question 7

What is cleavage?

Answer 7

Rapid mitotic cell division, following fertilisation. This isn’t a growth process.

Question 8

What is parthenogenesis?

Answer 8

Process where an unfertilised egg develops into a new individual.

Question 9

Describe the bilaminar germ disc

Answer 9

Cells are organised into two layers: the epiblast and hypoblast. These are surrounded by an exocoelomic cavity. This establishes the dorsal-ventral axis of the embryo.

Question 10

What is gastrulation?

Answer 10

The process of epiblastic cell movement that leads to the transformation of the bilaminar germ disc to the trilaminar germ disc.
It commences with the formation of the primative streak, through which the epiblastic cells invaginate to form the mesoderm and endoderm. The remaining epiblastic cells become the endoderm.

Question 11

What is caudal dysplasia? What complications may occur?

Answer 11

A congential defect in which the development of the lower spine is abnormal.
Fusion of lower limbs, vertebral abnormalities, renal agensis, imperforate anus and abnormalities of genital organs.

Question 12

What is situs invertus?

Answer 12

A congenital condition in which the major visceral organs are reversed or mirrored from their normal position.

Question 13

What is morphogenesis?

Answer 13

Form-shaping process in an embryo that results in differential tissue growth

Question 14

What is normogenesis?

Answer 14

The normal formation of cells and tissues.

Question 15

What is dysmorphogenesis?

Answer 15

The formation of abnormal tissue.

Question 16

What is a malformation? What are they caused by?

Answer 16

Primary morphologic defect in an organ or body part that results from a disturbance of developmental events directly involved in the formation of a particular structure.
Can be caused by environmental and/or genetic factors acting independently or together.

Question 17

What is a deformation?

Answer 17

Secondary morphologic defect imposed upon and organ or body part due to mechanical forces over a prolonged period of time.

Question 18

What is a disruption?

Answer 18

Morphologic alteration of already formed structures due to destructive processes.

Question 19

What is a malformation syndrome?

Describe down Syndrome and fetal alcohol syndrome.

Answer 19

When dysmorphogenesis occurs as a pattern of well characterised, primary malformations appearing together in a predictable fashion.
Down Syndrome - Flat facial features, small nose, reduced muscle tone, slant to the eye, enlarged tounge, single deep crease across the centre of the palm and hyperflexibility.
Fetal alcohol syndrome - Short palpebral fissure length, smooth philtrum, thin upper lip, brain damage.

Question 20

What is teratology?

What is a teratogen?

Answer 20

Teratology - The study of birth defects or congenital malformations
Teratogen - Any factor/agent that causes a birth defect or congential malformation.