Term
|
Definition
Groove forms along middle back
Neural Tube froms from closure of neural groove |
|
|
Term
2-3 weeks
2 mm C-R
Cardiovascular |
|
Definition
Beginning of blood circulation
Tubular heart begins to form at end of this period |
|
|
Term
|
Definition
|
|
Term
2-3 weeks
2 mm C-R
Genitourinary |
|
Definition
| Formation of kidneys beginning |
|
|
Term
2-3 weeks
2 mm C-R
Respiratory |
|
Definition
|
|
Term
2-3 weeks
2 mm C-R
Endocrine |
|
Definition
|
|
Term
|
Definition
Optic cup and lens pit have formed
Pigment in eyes |
|
|
Term
|
Definition
| Auditory pit is now enclosed structure |
|
|
Term
|
Definition
|
|
Term
|
Definition
Anterior portion of neural tube closes to form brain
Closure of posterior end forms spinal cord |
|
|
Term
4 weeks
4-6 mm C-R
Musculoskeletal |
|
Definition
|
|
Term
4 weeks
4-6 mm C-R
Cardiovascular |
|
Definition
Tubular heart beats by the end of this period
Primitive red blood cells circulate through fetus/chorionic villi |
|
|
Term
|
Definition
Mouth: formation of oral cavity
Primitive jaws present
Esophagotracheal septum begins division of esophagus and trachea
Stomach forms
Esophagus and intestine become tubular
Ducts of pancreas and liver forming |
|
|
Term
|
Definition
| Only 0.5 % of total body weight is fat |
|
|
Term
|
Definition
Brain has differentiated
Cranial nerves present |
|
|
Term
5 weeks
8 mm C-R
Musculoskeletal |
|
Definition
| Developing muscles have innervation |
|
|
Term
5 weeks
8 mm C-R
Cardiovascular |
|
Definition
| Atrial division has occurred |
|
|
Term
6 weeks
12 mm C-R
Musculoskeletal |
|
Definition
Bone rudiments present
Primitive skeletal shape forming
Muscle mass begins to develop
Ossification of skull and jaws begins |
|
|
Term
6 weeks
12 mm C-R
Cardiovascular |
|
Definition
Chambers present in heart
Groups of blood cells can be identified |
|
|
Term
|
Definition
Oral and nasal cavities and upper lip formed
Liver begins to form red blood cells |
|
|
Term
6 weeks
12 mm C-R
Respiratory |
|
Definition
| Trachea, bronchi, and lung buds present |
|
|
Term
|
Definition
| Formation of external, middle, and inner ear continues |
|
|
Term
6 weeks
12 mm C-R
Sexual Development |
|
Definition
| Embryonic sex glands appear |
|
|
Term
7 weeks
18 mm C-R
Cardiovascular |
|
Definition
| Fetal heartbeats can be detected |
|
|
Term
|
Definition
Mouth: tongue separates; palate folds.
Digestive tract: stomach attains final form |
|
|
Term
7 weeks
18 mm C-R
Genitourinary |
|
Definition
| Separation of bladder and urethra from rectum |
|
|
Term
7 weeks
18mm C-R
Respiratory |
|
Definition
| Diaphragm separates abdominal and thoracic cavities |
|
|
Term
|
Definition
Optic nerve formed
Eyelids appear
Thickening of lens |
|
|
Term
7 weeks
18 mm C-R
Sexual developement |
|
Definition
| Differentiation of sex glands into ovaries and testes begins |
|
|
Term
8 weeks
2.5 - 3 cm. C-R
Weight |
|
Definition
|
|
Term
8 weeks
2.5-3 cm C-R
Musculoskeletal |
|
Definition
Digits formed
Further differentiation of primitive skeleton
Cartilaginous bones show first signs of ossification
Development of muscles in trunk, limbs, head
Some movement of fetus is now possible |
|
|
Term
8 weeks
2.5 - 3 cm C-R
Cardiovascular |
|
Definition
Development of heart essentially complete
Fetal circulation follows two circuits - four extraembryonic and two intraembryonic
Heartbeat can be heard with doppler anywhere from the end of this week up until the next 4 weeks |
|
|
Term
|
Definition
Mouth: completion of lip fusion
Digestive tract: rotation in midgut
Anal membrane has perforated |
|
|
Term
8 weeks
2.5 - 3 cm. C-R
Ears |
|
Definition
| External, middle, and inner ear assuming final form |
|
|
Term
8 weeks
2.5 -3 cm. C-R
Sexual development |
|
Definition
| Male and female external genitals appear similar until end of the next week |
|
|
Term
|
Definition
|
|
Term
10 weeks
5-6 cm. C-R
Nervous |
|
Definition
Neurons appear at caudal end of spinal cord
Basic divisions of brain present |
|
|
Term
10 weeks
5-6 cm. C-R
Musculoskeletal |
|
Definition
| Fingers and toes begin nail growth |
|
|
Term
|
Definition
Mouth: separation of lips from jaw; fusion of palate folds
Digestive tract: developing intestines enclosed in abdomen |
|
|
Term
10 weeks
5-6 cm. C-R
Genitourinary |
|
Definition
|
|
Term
10 weeks
5-6 cm. C-R
Endocrine |
|
Definition
| Islets of Langerhans differentiated |
|
|
Term
|
Definition
Eyelids fused closed
Development of lacrimal duct |
|
|
Term
10 weeks
5-6 cm. C-R
Sexual Development |
|
Definition
| Males: production of testosterone and physical characteristics during the two week prior to and following this time. |
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
Weight |
|
Definition
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
Musculoskeletal |
|
Definition
Clear outlining of miniature bones from this week up to 20 weeks
Process of ossification is established throughout the fetal body
Appearance of involuntary muscles in viscera |
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
GI |
|
Definition
Mouth: completion of palate
Digestive tract: appearance of muscles in gut; bile secretion begins; liver is major producer of red blood cells |
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
Respiratory |
|
Definition
| Lungs acquire definitive shape |
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
Skin |
|
Definition
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
Endocrine |
|
Definition
| Hormonal secretion from thyroid; insulin present in pancreas |
|
|
Term
12 weeks
8 cm C-R; 11.5 cm C-H
Immunologic |
|
Definition
| Appearance of lymphoid tissue in fetal thymus gland |
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
Weight |
|
Definition
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
Musculoskeletal |
|
Definition
| Teeth beginning to form hard tissue that will become central incisors |
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
GI |
|
Definition
Mouth: differentiation of hard and soft palate
Digestive tract: development of gastric and intestinal glands; intestines begin to collect meconium |
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
Genitourinary |
|
Definition
| Kidneys assume typical shape and organization |
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
Skin |
|
Definition
Appearance of scalp hair, lanugo present on body
Transparent skin with visible blood vessels
Sweat glands developing |
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
Eyes, ears, nose: |
|
Definition
|
|
Term
16 weeks
13.5 cm C-R; 15 cm C-H
Sexual Development |
|
Definition
| Sex determination possible |
|
|
Term
|
Definition
| Teeth beginning to form hard tissue - enamel and dentine that will become the lateral incisors |
|
|
Term
|
Definition
| Fetal heart tones audible with fetoscope at up to two weeks prior or two weeks after this week. |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
Weight |
|
Definition
| 435 g (6% of total body weight is fat) |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
Nervous |
|
Definition
| Myelination of spinal cord begins |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
Musculoskeletal |
|
Definition
Teeth beginning to form hard tissue that will become canine and first molar.
Lower limbs are of final relative proportions |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
GI |
|
Definition
Fetus actively sucks and swallows amniotic fluid
Peristaltic movements begin |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
Skin |
|
Definition
Lanugo covers entire body
Brown fat begins to form
Vernix caseosa begins to form |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
Immunologic |
|
Definition
| Detectable levels of fetal antibodies (IgG) |
|
|
Term
20 weeks
19 cm. C-R; 25 cm. C-H
Blood formation |
|
Definition
| Iron is stored and bone marrow is increasingly important |
|
|
Term
24 weeks
23 cm C-R; 28 cm. C-H
Weight |
|
Definition
|
|
Term
24 weeks
23 cm C-R; 28 cm. C-H
Nervous |
|
Definition
| Brain looks like mature brain |
|
|
Term
24 weeks
23 cm C-R; 28 cm. C-H
Musculoskeletal |
|
Definition
| Teeth are beginning to form hard tissue that will become the second molars |
|
|
Term
24 weeks
23 cm C-R; 28 cm. C-H
Respiratory |
|
Definition
Respiratory movements may occur anywhere from this week up to 40 weeks
Nostrils open
Alveoli appear in lungs and begin production of surfactant
Gas exchange possible |
|
|
Term
24 weeks
23 cm C-R; 28 cm. C-H
Skin |
|
Definition
Reddish and wrinkled
Vernix caseosa present |
|
|
Term
24 weeks
23 cm C-R; 28 cm. C-H
Immunologic |
|
Definition
| IgG levels reach maternal levels |
|
|
Term
28 weeks
27 cm. C-R; 35 cm. C-H
Weight |
|
Definition
|
|
Term
28 weeks
27 cm. C-R; 35 cm. C-H
Nervous |
|
Definition
| Begins regulation of some body functions |
|
|
Term
28 weeks
27 cm. C-R; 35 cm. C-H
Skin |
|
Definition
Adipose tissue accumulates rapidly
Nails appear
Eyebrows and eyelashes present |
|
|
Term
28 weeks
27 cm. C-R; 35 cm. C-H
Eyes |
|
Definition
| Eyelids open between 2 weeks prior to this week up to one week after this week |
|
|
Term
28 weeks
27 cm. C-R; 35 cm. C-H
Sexual development |
|
Definition
| Males: testes descend into the inguinal canal and upper scrotum |
|
|
Term
32 weeks
31 cm C-R; 38-43 C-H
Weight |
|
Definition
|
|
Term
32 weeks
31 cm C-R; 38-43 C-H
Nervous |
|
Definition
|
|
Term
36 weeks
35 cm C-R; 48-52 cm C-H
Weight |
|
Definition
|
|
Term
36 weeks
35 cm C-R; 48-52 cm C-H
Musculoskeletal |
|
Definition
| Distal femoral ossification centers present |
|
|
Term
36 weeks
35 cm C-R; 48-52 cm C-H
Skin |
|
Definition
Pale
Body rounded with lanugo disappearing
Hair fuzzy or wooly
Few sole creases
Sebaceous glands active and helping to produce vernix caseosa from now until 40 weeks |
|
|
Term
36 weeks
35 cm C-R; 48-52 cm C-H
Ears |
|
Definition
| Earlobes soft with little cartilage |
|
|
Term
36 weeks
35 cm C-R; 48-52 cm C-H
Sexual development |
|
Definition
Males: scrotum small and few rugae present
Descent of testicles into upper scrotum to stay (between now and 40 weeks)
Females: labia majora and minora equally prominent |
|
|
Term
38-40 weeks
40 cm. C-R; 48-52 cm. C-H
Weight |
|
Definition
| 3200 + grams (16% of total body weight is fat) |
|
|
Term
38-40 weeks
40 cm. C-R; 48-52 cm. C-H
Respiratory |
|
Definition
| Lecithin-sphingomyelin (L/S) ration approaches 2:1 (this indicates decreased risk of respiratory distress from inadequate surfactant production if born now) |
|
|
Term
38-40 weeks
40 cm. C-R; 48-52 cm. C-H
Skin |
|
Definition
Smooth and pink
Vernix present in skin folds
Moderate to profuse silky hair
Lanugo on shoulders and upper back
Nails extend over tips of digits
Creases cover sole |
|
|
Term
38-40 weeks
40 cm. C-R; 48-52 cm. C-H
Ears |
|
Definition
| Earlobes firmer because of increased cartilage |
|
|
Term
38-40 weeks
40 cm. C-R; 48-52 cm. C-H
Sexual development |
|
Definition
Males: rugous scrotum
Females: labia majora well developed and minor small or completely covered |
|
|
