Introduction to Human Embryology

Question 1

What is embryology? How long does it take?

Answer 1

A developmental process that starts from a single cells and ends with a fully grown baby. It takes 38 weeks/266 days.

Question 2

What did scientists previously believe about the process of fertilization?

Answer 2

They believed that a miniature human being hid within the spermatozoon/sperm and grew once the sperm made contact with an ovum.

Question 3

What are the basic structures needed for a successful pregnancy?

Answer 3

1. Intact male and female reproductive organs
2. Spermatozoon/sperm
3. Ovum

Question 4

What does sperm’s structure consist of?

Answer 4

1. Acrosome
2. Head
3. Nucleus
4. Neck
5. The tail (middle, principal, and end pieces of the tail)

Question 5

What does ova structure consist of?

Answer 5

1. Follicular cells of corona radiata
2. Zona pellucida
3. Nucleus
4. Cytoplasm

Question 6

Explain the term situs solitus

Answer 6

The normal arrangement of internal organs

Question 7

Explain the term situs inversus

Answer 7

An abnormality/disturbance in the arrangement of internal organs AKA mirror image

Question 8

Explain a case in which situs inversus will preserve normal function

Answer 8

If the whole system is inverted, the function of the system will be maintained.

Question 9

What is the stage that occurs due to the union of female and male gametes? And what does it form?

Answer 9

Fertilization. Gamete.

Question 10

True or False
The meiotic division of the zygote results in the formation of embryonic cells called blastocysts.

Answer 10

False
The meiotic division of the zygote results in the formation of embryonic cells called blastocysts.

Correction: The mitotic division of the zygote results in the formation of embryonic cells called blastomeres.

Question 11

How many embryonic cells does the morula contain? When does it occur?

Answer 11

12 embryonic cells. 3-4 days after fertilization.

Question 12

What are the stages of development?

Answer 12

1. Fertilization
2. Embryogenesis
   a. Cleavage
   b. Morula
   c. Blastocyst
3. fetal period

Question 13

What are the key characteristics of embryogenesis/organogenesis?

Answer 13

1. It occurs during the first 8 weeks of development (following fertilization)
2. Most development occurs during this process, so if an abnormality occurs, it would most likely be during this period.
3. The primordia of all major structures are developed

Question 14

What are the key characteristics of the fetal period

Answer 14

1. Differentiation of primordia
2. Growth of the fetus
3. Occurs during the 9th to 38th weeks of pregnancy

Question 15

When does ovulation occur?

Answer 15

2 weeks following the onset of the last normal menstrual period (LMNP)

Question 16

What are teratogens? List some examples of teratogens.

Answer 16

Any agent that could cause a mutation/alteration in or interfere with normal development e.g. radiation (x-ray) and alcohol.

Question 17

Danielle is a surrogate pregnant woman. She came into Dr Samira’s office and asked about her expected delivery date. She said that her sister will be getting married on August 30th, and she’s afraid she’s going to have to miss it. Dr Samira asked her when her last normal menstrual period was, but Danielle forgot to log it down. She did remember, however, that her previous gynecologist informed her that the in vitro fertilization of her ovum occured on the 2nd of January. Dr Samira told her not to worry as she is expected to give birth on ——–. It was a leap year.

Answer 17

September 24th, or 10-14 days within this date

Question 18

Danielle gave birth on September 1st. Considering her calculated delivery date being September 24th, was her baby born postmaturely or prematurely?

Define premature and postmature.

Answer 18

Her baby was born prematurely because it was born more than two weeks before the calculated delivery date.

Premature: born two weeks before the calculated delivery date.

Postmature: Born two weeks after the calculated delivery date.

Question 19

What is polydactyly?

Answer 19

Having an extra digit (finger/toe).

Question 20

What are the types of polydactyly? What are the types classified based on?

Answer 20

They are classified based on the location of the extra digit.

1. Pre-axial polydactyly: the extra digit is located outside the big toe/thumb.
   a. When it is outside the thumb, it is called: radial polydactyly
   b. When it is outside the big toe, it is called, tibial polydactyly
2. Central polydactyly: the extra digit is located between toes/fingers.
3. Post-axial polydactyly: the extra digit is located outside the little finger/little toe.
   a. When it is outside the little finger, it is called: ulnar polydactyly
   b. When it is outside the little toe, it is called: fibular polydactyly

Question 21

What is the condition that is characterized by webbed/wedge-shaped fingers at birth? What are the most fingers that most commonly fuse?

Answer 21

Syndactyty. The middle and ring fingers.

Question 22

What plane is a median section cut along?

Answer 22

The sagittal plane

Question 23

Define caudal.

Answer 23

Toward the tail/posterior aspect of the body.

Question 24

True or false
Anterior and dorsal are synonyms

Answer 24

False

Anterior and dorsal are synonyms
Correction:
1. Anterior and dorsal are antonyms

Anterior and dorsal are synonyms
2. Anterior and ventral are synonyms.