3: Embryogenesis and Development

Question 1

SEQ human fertilization

Answer 1

Sperm and egg meet in ampulla of fallopian tube
Acrosomal enqymes penetrate corona radiata and zona pellucida
On contact with egg plasma membrane, acrosomal apparatus injects sperm pronucleus
=> this causes egg acivation. Calcium ions initiate slow block corticol reaction.

Question 2

Describe cell division during cleavage

Answer 2

Total size constant, but cells divide.

Question 3

When does zygote become embryo?

Answer 3

After first cleavage

Question 4

What is a morula?

Answer 4

Solid mass of cells seen in early development

Question 5

Ectoderm gives rise to what?

Answer 5

Epidermis, hair, nails
Epithelium of nose, mouth, anal canal
Nervous system, including adrenal medulla
Lens of the eye

Question 6

Mesoderm gives rise to what?

Answer 6

Musculoskeletal system
Circulatory system
Excretory system
Muscle/connective tissue in digestion/respiration
Gonads
Adrenal cortex

Question 7

Endoderm gives rise to what?

Answer 7

Epithelia of respiratory system, digestive tract

Pancreas, thyroid, bladder, urinary tracts

Question 8

SEQ Neurulation

Answer 8

Notochord induces overlaying ectoderm to form neural folds => these fold to form neural tube => tip of each contains neural crest cells, which become PNS and also specific cell types across body, e.g. calcitonin-producing cells in thyroid

Question 9

What a teratogens?

Answer 9

Substances that interfere with development, e.g. alcohol, some drugs, viruses, bacteria, environment

Question 10

How does cell specialization start?

Answer 10

Uneven mitosis

Morphogens - promote specialization, provided cell has required competency to respond

Question 11

What is the difference between totipotent, pluripotent, multipotent cells?

Answer 11

Totipotent – can develop into any kind of cell, including three germ layers and placental structures
Pluripotent – can develop into any of three germ layers
Multipotent – can develop into specific subset of cell types

Question 12

Define autocrine, paracrine, juxtacrine, endocrine

Answer 12

Crine = signal

Para - next; juxta - adjacent, etc

Question 13

What is apoptosis?

Answer 13

Programmed cell death via formation of apoptotic cell clebs, which can subsequently be absorbed and digested by neighboring cells. Can be used for sculpting, e.g. removing web between digits

Question 14

What is the difference between adult hemoglobin and fetal hemoglobin?

Answer 14

Fetal - HbF - has higher affinity for oxygen than HbA – assists transfer into fetal circulatory system

Question 15

Which direction does blood flow in umbilical arteries/veins?

Answer 15

Umbilical arteries – carry deoxygenated blood from fetus to placenta
Umbilical veins - carry oxygenated blood from placenta to fetus

Question 16

Which fetal organs are most inactive?

Answer 16

Lungs, liver

Question 17

What are the three shunts of the fetal circulatory system?

Answer 17

Formen ovale - connects right atrium to left atrium – bypasses lungs
Ductus arteriosus - connects pulmonary artery to aorta – bypasses lungs
Ductus venous - connects umbilical vein to inferior vena cava - bypasses liver

Question 18

What are the two main cell groups of a blastocyst?

Answer 18

Trophoblast - gives rise to chorion and placenta

Inner cell mass – gives rise to fetus

Question 19

Define:
Chorion
Yolk sac
Allantois
Amnion

Answer 19

Chorion - villi penetrate endometrium
Yolk sac - supports embryo before placenta established
Allantois - involved in early fluid exchange between embryo and yolk sac
Amnion - inside chorion, produces amniotic fluid