[5] PRELIMS | MILESTONES OF FETAL DEVELOPMENT

Question 1

The embryonic stage starts on ____ and continues until approximately the ____

Answer 1

starts on day 15; continues until the 8th week

Question 2

3 Weeks - Embryonic disk becomes ____ and ____-shaped, with a ____ cephalic end and ____ caudal end

Answer 2

Embryonic disk becomes elongated and pear-shaped, with a broad cephalic end and narrow caudal end

Question 3

3 Weeks - ____ has formed a long ____ tube for ____

Answer 3

Ectoderm has formed a long cylindrical tube for brain and spinal cord development

Question 4

3 Weeks - ____ from the endoderm appear as a ____

Answer 4

GIT from the endoderm appear as a tube-like structure

Question 5

3 Weeks - the most advanced organ is the:

Answer 5

Heart

Question 6

4-5 Weeks - during days ____, the ____ (or a series of mesodermal blocks) form on either side of the embryo’s midline

Answer 6

During days 21 to 32, the somites (or a series of mesodermal blocks) form on either side of the embryo’s midline

Question 7

4-5 Weeks - Prior to ____, arm and leg buds are ____, but the tail bud is ____

Answer 7

Prior to 28 days, arm and leg buds are not visible, but the tail bud is present

Question 8

4-5 Weeks: The pharyngeal arches – which will form the ____, ____, and ____ – develop at this time

Answer 8

The pharyngeal arches – which will form the lower jaw, hyoid bone, and larynx – develop at this time

Question 9

4-5 Weeks - The ____ appear now; these pouches will form the ____ and cavity of the ____, the ____, and the ____

Answer 9

The pharyngeal pouches appear now; these pouches will form the eustachian tube and cavity of the middle ear, the tonsils, and the parathyroid and thymus glands

Question 10

4-5 Weeks - The primordial of the ____ are also present

Answer 10

The primordial of the ear and eye are also present

Question 11

4-5 Weeks - During the ____, the ____ of the eye form and the ____ develop

Answer 11

During the fifth week, the optic cups and lens vessels of the eye form and the nasal pits develop

Question 12

4-5 Weeks - Partitioning in the heart occurs with the dividing of the ____

Answer 12

Partitioning in the heart occurs with the dividing of the atrium

Question 13

4-5 Weeks - Embryo has marked ____ body, accentuated by the ____ and the large head folded over a ____

Answer 13

Embryo has marked C-shaped body, accentuated by the rudimentary tail and the large head folded over a protuberant trunk

Question 14

4-5 Weeks - By ____, the arm and leg buds are well developed, with ____ and foot plates. The ____, ____, and ____ show the most advanced development

Answer 14

By day 35, the arm and leg buds are well developed, with paddle-shaped hand and foot plates. The heart, circulatory system, and brain show the most advanced development

Question 15

4-5 Weeks - Brain has differentiated into ____ areas, and ____ pair of cranial nerves are recognizable

Answer 15

Brain has differentiated into five areas, and 10 pair of cranial nerves are recognizable

Question 16

6 Weeks:
* ____ are more highly developed
* Trunk is ____ than in earlier stages
* ____ are recognizable

Answer 16

• Head structures are more highly developed
• Trunk is straighter than in earlier stages
• Upper and lower jaws are recognizable

Question 17

6 Weeks:
* ____ are well formed
* ____ has developed and its caudal end is bifurcated for beginning ____

Answer 17

• External nares are well formed
• Trachea has developed and its caudal end is bifurcated for beginning lung formation

Question 18

6 Weeks:
* ____ has formed
* ____ is developing
* ____ are developing rapidly

Answer 18

• Upper lip has formed
• Palate is developing
• Ears are developing rapidly

Question 19

6 Weeks:
* ____ now has most of its definitive characteristics, and ____ begins to be established
* ____ starts to produce blood cells

Answer 19

• Heart now has most of its definitive characteristics, and fetal circulation begins to be established
• Liver starts to produce blood cells

Question 19

6 Weeks:
* Arms have begun to extend ____, and both arms and legs have ____, although they may still be webbed
* There is a ____ in the arms, which are more advanced in development than the legs
* Beginning at this stage, the prominent tail will ____

Answer 19

• Arms have begun to extend ventrally across the chest, and both arms and legs have digits, although they may still be webbed
• There is a slight elbow bend in the arms, which are more advanced in development than the legs
• Beginning at this stage, the prominent tail will recede

Question 20

7 Weeks:
* Head of the embryo is rounder and nearly erect
* Eyes have shifted and are closer together
* Eyelids are beginning to form

Question 20

7 Weeks: Prior to this time, the ____ formed one tube that ended in a blind pouch; they now separate into two tubular structures

Answer 20

Prior to this time, the rectal and urogenital passages formed one tube that ended in a blind pouch; they now separate into two tubular structures

Question 21

7 Weeks: Intestines enter the ____ in the area of the umbilical cord (called ____). At this point, the beginnings of all essential external and internal structures are present.

Answer 21

Intestines enter the extraembryonic coelom in the area of the umbilical cord (called umbilical herniated). At this point, the beginnings of all essential external and internal structures are present.

Question 22

8 Weeks:
* Approximately ____ C-R
* Clearly resembles a human being
* ____ continue to develop
* ____ begin to fuse
* ____ of the external ears begin to assume final shape, but are still set low

Answer 22

• Approximately 3 cm (1.2 in) long C-R
• Clearly resembles a human being
• Facial features continue to develop
• Eyelids begin to fuse
• Auricles of the external ears begin to assume final shape, but are still set low

Question 23

8 Weeks: * External genitals appear, but ____ * ____ opens with the perforation of the ____

Answer 23

* External genitals appear, but **sex not clearly identifiable** * **Rectal passage** opens with the perforation of the **anal membrane**

Question 24

8 Weeks: * Circulatory system through the umbilical cord is ____ * ____ are beginning to form * Large muscles are now capable of ____

Answer 24

* Circulatory system through the umbilical cord is **well-established** * **Long bones** are beginning to form * Large muscles are now capable of **contracting**

Question 25

**9-12 Weeks**: * At end of 9 weeks, fetus reaches a C-R length of ____ and weighs about ____ * Head is large and comprises ____ * At 12 weeks, the fetus reaches ____ C-R and weighs about ____. * Face is ____, with the nose protruding, the chin small and receding, and the ear acquiring a more adult shape * Eyelids close at about ____ and will not reopen until about the ____ * Some reflex movement of the lips suggestive of the ____ has been observed at ____. * Tooth buds now appear * Limbs are ____, with well-formed digits.

Answer 25

* At end of 9 weeks, fetus reaches a C-R length of **5 cm (2 in)** and weighs about **14 grams** * Head is large and comprises **almost half of the fetus’ entire size** * At 12 weeks, the fetus reaches **7 to 8 cm** C-R and weighs about **45 g (1.6 oz)**. * Face is **well-formed**, with the nose protruding, the chin small and receding, and the ear acquiring a more adult shape * Eyelids close at about **10th week** and will not reopen until about the **28th week** * Some reflex movement of the lips suggestive of the **sucking reflex** has been observed at **3 months**. * Tooth buds now appear * Limbs are **long and slender**, with well-formed digits.

Question 26

9-12 Weeks: * Fetus can ____ toward the palm and begins to make a tiny fist * Legs are still ____ than the arms * ____ completes its development * Well-differentiated ____ appear * ____ begin to produce urine * ____ of the fetus now occur * FHR can be ascertained by electronic devices between ____ weeks. ( ____ bpm)

Answer 26

* Fetus can **curl fingers** toward the palm and begins to make a tiny fist * Legs are still **shorter and less developed** than the arms * **Urogenital tract** completes its development * Well-differentiated **genitals** appear * **Kidneys** begin to produce urine * **Spontaneous movements** of the fetus now occur * FHR can be ascertained by electronic devices between **8 and 12 weeks**. (**120-160** bpm)

Question 27

**13-16 Weeks:** * A period of ____ * At 13 weeks, fetus weighs ____ and is about ____ in C-R length * ____, or fine hair, begins to develop, especially on the head. * Skin is ____ * More muscle tissue and body skeleton have ____ and hold the fetus ____ * ____ movements are present * Fetus ____ arms and legs: makes sucking motions, swallows ____, and produces ____ in the ____ * By the beginning of ____, ____ is clearly identifiable

Answer 27

* A period of **rapid growth** * At 13 weeks, fetus weighs **55 to 120 g** and is about **10 to 17 cm** in C-R length * **Lanugo**, or fine hair, begins to develop, especially on the head. * Skin is **so transparent** * More muscle tissue and body skeleton have **developed** and hold the fetus **more erect** * **Active** movements are present * Fetus **stretches and exercises** arms and legs: makes sucking motions, swallows **amniotic fluid**, and produces **meconium** in the **intestinal tract** * By the beginning of **week 16**, **skeletal ossification** is clearly identifiable

Question 28

**20 Weeks**: * Fetus doubles its C-R length and now measures ____ * Fetal weight is ____ * Lanugo covers the ____ and is especially prominent on the ____ * Subcutaneous deposits of ____, which has rich blood supply, make the skin less transparent * ____ now appear over the mammary glands * Head is covered with ____, and the ____ are beginning to form * ____ are present on both fingers and toes * Muscles are ____, and fetus is active * Quickening is felt * Fetal heartbeat audible through a ____

Answer 28

* Fetus doubles its C-R length and now measures **25 cm long** * Fetal weight is **223 g** * Lanugo covers the **entire body** and is especially prominent on the **shoulders** * Subcutaneous deposits of **brown fat**, which has rich blood supply, make the skin less transparent * **Nipples** now appear over the mammary glands * Head is covered with **fine, woolly hair**, and the **eyebrows and eyelashes** are beginning to form * **Nails** are present on both fingers and toes * Muscles are **well-developed**, and fetus is active * Quickening is felt * Fetal heartbeat audible through a **fetoscope**

Question 29

**24 Weeks**: * The fetus at 24 weeks reaches a crown-to-heel (C-H) length of ____ * Weighs about ____. * Hair on the head is ____, and eyebrows and eyelashes ____ * Eye is ____ and will soon open * Fetus has a ____ and by the end of 6 months, has ____ * Skin covering the body is ____, with little subcutaneous fat * Skin on hands and feet have ____, with skin ridges on palms and soles forming distinct ____ * Skin over entire body is covered with ____ * ____ in the lungs just beginning to form

Answer 29

* The fetus at 24 weeks reaches a crown-to-heel (C-H) length of **28 to 36 cm** * Weighs about **550 to 600 g**. * Hair on the head is **growing long**, and eyebrows and eyelashes **have formed** * Eye is **structurally complete** and will soon open * Fetus has a **reflex hand grip (grasp reflex)** and by the end of 6 months has **startle reflex** * Skin covering the body is **reddish and wrinkled**, with little subcutaneous fat * Skin on hands and feet have **thickened**, with skin ridges on palms and soles forming distinct **foot and fingerprints** * Skin over entire body is covered with **vernix caseosa** * **Alveoli** in the lungs just beginning to form

Question 29

**25-28 Weeks**: * At ____, fetal skin is still red, wrinkled, and covered with ____ * During this time, brain is developing rapidly, and the nervous system is complete enough to provide some ____ * Eyelids open and close under ____ * In the male fetus, testes begin to descend into the ____ * Respiratory and circulatory systems have developed though ____ still physiologically immature * Fetus at 28 weeks is about ____ long C-H and weighs ____ (2 lbs, 10.5 oz to 2 lbs, 12 oz).

Answer 29

* At **6 months**, fetal skin is still red, wrinkled, and covered with **vernix caseosa** * During this time, brain is developing rapidly, and the nervous system is complete enough to provide some** degree of regulation of body functions** * Eyelids open and close under **neural control** * In the male fetus, testes begin to descend into the **scrotal sac** * Respiratory and circulatory systems have developed though **lungs** still physiologically immature * Fetus at 28 weeks is about **35 to 38 cm (14 to 15 in)** long C-H and weighs **1200 to 1250 g** (2 lbs, 10.5 oz to 2 lbs, 12 oz).

Question 30

**29-32 Weeks**: * At 30 weeks, pupillary light reflex is present * Fetus is gaining weight from an increase in body muscle and fat, and weighs about 1600 g, with a C-H length of about 38 to 43 cm (15 to 17 in) by 32 weeks of age * CNS has matured enough to direct rhythmic breathing movements and partially control body temperature though lungs are not yet fully mature * Bones are fully developed but soft and flexible * Fetus begins storing iron, calcium, and phosphorus * In males, the testicles may be located in the scrotal sac but often still high in the inguinal canals

Answer 30

* At 30 weeks, pupillary light reflex is present * Fetus is gaining weight from an increase in body muscle and fat, and weighs about 1600 g, with a C-H length of about 38 to 43 cm (15 to 17 in) by 32 weeks of age * CNS has matured enough to direct rhythmic breathing movements and partially control body temperature though lungs are not yet fully mature * Bones are fully developed but soft and flexible * Fetus begins storing iron, calcium, and phosphorus * In males, the testicles may be located in the scrotal sac but often still high in the inguinal canals

Question 31

**35-36 Weeks**: * Fetus begins to ____, and ____ covers the deposits of subcutaneous fat * Lanugo begins to ____ * Nails reach the ____ * By ____ weeks of age, fetus has a ____ and exhibits ____ * By ____ weeks of age, weight is usually ____ (5 to 6 lb), and C-H length is about ____.

Answer 31

* Fetus begins to **get plump**, and **less wrinkled skin** covers the deposits of subcutaneous fat * Lanugo begins to **disappear** * Nails reach the **edge of fingertips** * By **35 weeks of age**, fetus has a **firm grasp** and exhibits **spontaneous orientation to light** * By **36 weeks of age**, weight is usually **1,800 to 2,700 g** (5 to 6 lb), and C-H length is about **42 to 48 cm**.

Question 32

**38-40 Weeks**: * Considered ____ at 38 weeks and up to 40 weeks after conception * C-H length varies from ____ (19 to 21 in) * Weight at term is about ____ (6 lb, 10 oz to 7 lb, 15 oz) * Skin is ____ and has a ____ * The only lanugo left is on the ____ * Hair on the head is ____ but is coarse and about 1 in long * Vernix caseosa is ____

Answer 32

* Considered **full term** at 38 weeks and up to 40 weeks after conception * C-H length varies from **48 to 52 cm** (19 to 21 in * Weight at term is about **3000 to 3600 g** (6 lb, 10 oz to 7 lb, 15 oz) * Skin is **pink** and has a **smooth, polished look** * The only lanugo left is on the **upper arms and shoulders** * Hair on the head is **no longer woolly** but is coarse and about 1 in long * Vernix caseosa is **present**

Question 33

**38-40 Weeks**: * Body and extremities are ____, with good ____, and fingernails extend ____ * Chest is ____ but still a smaller than the head, and mammary glands ____ * In males, the testes are in the ____ * As the fetus enlarges, amniotic fluid diminishes to about ____, and the fetal body mass ____ * Fetus assumes what is called its ____

Answer 33

* Body and extremities are **plump**, with good **skin turgor**, and fingernails extend **beyond the fingertips** * Chest is **prominent** but still a smaller than the head, and mammary glands **protrude in both sexes** * In males, the testes are in the **scrotum or palpable in the inguinal canals**. * As the fetus enlarges, amniotic fluid diminishes to about **500 mL or less**, and the fetal body mass fills the uterine cavity * Fetus assumes what is called its **position of comfort, or lie**