|
Fifth Week
|
Timing
|
Source |
The esophagus is developing.
|
Early in the 5th week of development |
Larsen, p 249 |
| The kidneys begin to develop. |
Early in 5th week after fertilization |
England, p 153 |
|
The trachea is developing.
|
Early in the 5th week of development |
Larsen, p 249 |
| The forelimbs and hindlimbs appear
as paddle-shaped buds. |
Beginning of 5th week |
Sadler, p 106 |
| The face begins to look human. |
5th week after conception |
Rugh, p 45 |
| Pain pathways run from sensory receptors
in the skin to those in the brain. Nerve endings
that sense pain are at least as dense in the skin
of a newborn as in an adult. Such receptors appear
around the mouth in the 5th week after conception,
and are present in the face, the palms, and the
soles of the feet by the 9th week, spreading to
the trunk, arms, and legs by the 13th week, and
to all areas of the skin by the 18th week. The development
of the neocortex, the largest part of the brain,
begins at 6 weeks after conception, and by 18 weeks
a full complement of nerve cells is present. The
evidence thus suggests that by late in gestation
the fetus has developed sufficiently to sense pain. |
from 5th week after conception |
Anand and Hickey, p 1322 & p 1326 |
| The jaws are forming. |
5th week after conception |
Rugh, p 45 |
| The permanent kidneys appear. |
5th week |
Sadler, p 305 |
| The pharynx is present. |
5th week after fertilization |
Rugh, p 45 |
| Liver ducts are forming. |
5th week after conception |
Rugh, p 46 |
| The pituitary gland is developing. |
5th week after ferilization |
Williams, p 178; Rugh, p 45 |
| The spleen is forming. |
5th week after conception |
Rugh, p 46 |
| The spleen is formed. |
5th week |
Larsen, p 159 |
| The trachea is developing. |
5th week after fertilization |
Moore, p 262 |
| The thyroid is developing. |
Late in 5th week |
Larsen, p 249 |
| The tongue is developing. |
Late in 5th week |
Larsen, p 249 |
| The penis and scrotum form. |
5th - 6th weeks |
Larsen, p 175 |
| Limb development takes place. |
5th - 8th weeks of development |
Larsen, p 209 |
| Leg buds are present. |
Day 29 after fertilization |
Sadler, front pages |
| The three primary parts of the brain
are present. |
Day 30 after conception |
Rugh, p 41 |
| The ears have started to form. |
Day 30 after conception |
Rugh, p 41 |
| The eyes have started to form. |
Day 30 after conception |
Rugh, p 41 |
| The lens pits and optic cups are forming. |
Day 30 after fertilization |
Moore, p 5 |
| The face is developing. |
Day 30 after fertilization |
Sadler, front pages |
| The gallbladder is developing. |
Day 30 of development |
Larsen, p 155 |
| Nasal placodes are present. |
Day 30 after fertilization |
Sadler, front pages |
| The nasal pits, which are the primordia
of the nostrils and the nasal cavaties, are forming. |
Day 30 after fertilization |
Moore, p 5 & p 239 |
| The nasal organs have begun forming. |
Day 30 after conception |
Rugh, p 41 |
| The stomach is forming. |
Day 30 |
Larsen, p 157 |
| The trachea is developing. |
Approximately day 30 after fertilization |
Rugh, p 43 |
| The intestines are defined. |
End of 1st month after conception |
Rugh, p 43 |
| The pancreas is defined. |
End of 1st month after conception |
Rugh, p 43 |
| The liver bud is present. |
End of 1st month |
Sadler, p 271 |
| The thyroid gland, which plays a critical
role in metabolism, begins developing. |
End of month 1 after conception |
Rugh, p 42 |
| The nervous, muscular, vascular, digestive,
and skeletal systems are in an incipient state. |
End of 1st month after conception |
Rugh, p 35 |
| The ears are forming. |
During the 2nd month |
Sadler, p 106 |
| The face is unmistakably human. |
2nd month after conception |
Rugh, p 54 |
| The nose is forming. |
During the 2nd month |
Sadler, p 106 |
| The skeleton is developing. |
2nd month after conception |
Rugh, p 52 |
| The face is forming. |
During 2nd month |
Sadler, p 106 |
| The limbs are forming. |
2nd month |
Sadler, p 106 |
| Great changes occur in appearance
because of the emergence of a disproportionately
large head and the formation of the limbs, face,
ears, nose, and eyes. |
During the 2nd month |
Sadler, p 106 |
| The esophagus (the food tube leading
to the stomach) begins to form. |
Day 31 after conception |
Rugh, p 43 |
| Leg buds begin to form. |
Day 31 after conception |
Rugh, p 43 |
| The primitive mouth is forming. |
Day 31 after fertilization |
Moore, p 5 |
| Muscles appear in the pelvic region. |
Day 31 after conception |
Rugh, p 43 |
| The stomach begins to form. |
Day 31 after conception |
Rugh, p 43 |
| The nasal pits are visible. |
Days 31-32 after fertilization |
Moore p 91 |
| Forelimbs are paddle-shaped. |
Days 31-35 of development |
Sadler, p 110 |
| The nasal pits are formed. |
Days 31-35 of development |
Sadler, p 110 |
| Coronary vessels appear. |
Day 32 after fertiliztaion |
Larsen, p xi |
| The primary intestinal loop forms. |
Day 32 after fertilization |
Larsen, p xi |
| The ventral pancreatic bud is present. |
Day 32 |
Larsen, p 157 |
| Spinal nerves begin to sprout. |
Day 32 after fertiliztion |
Larsen, p xi |
| The primary intestinal loop is forming. |
Approximately day 32 |
Sadler, p 281 |
| The larynx is developing. |
Approximately day 32 |
Sadler, p 281 |
| The palate is developing. |
About day 32 after fertilization |
Moore, p 98 |
| The pharynx is developing. |
About day 32 after fertilization |
Moore p 98 |
| The cerebral cortex, the part of the
brain that controls the intellect and motor activity,
begins to differentiate. |
Day 33 after conception |
Rugh, p 44 |
| Melanin first appears in the cells
of the developing pigment retina. |
Day 33 |
Larsen, p 257 |
| The forearm region can be distinguished. |
Day 33 of development |
Larsen, p 209 |
| Hand plates are present. |
Day 33 after fertilization |
Moore, p 5 |
| Hand plates are developing. |
Day 33 after fertilization |
Larsen, p xii |
| The shoulder region can be distinguished. |
Day 33 of development |
Larsen, p 209 |
| Hand plates are formed and digital
rays are present. |
Days 33-36 after fertilization |
Moore, p 91 |
| The cerebral vesicles are distinct. |
Day 34 after fertilization |
Moore, p 5 |
| The elbows are developing. |
Day 34 after fertilization |
Sadler, front pages |
| Foot plates are developing. |
Day 34 after fertilization |
Moore, p 5; Sadler, front pages |
| Hand plates are developing. |
Day 34 after fertilization |
Sadler, front pages |
| Echocardiography can detect heart
movements. |
About day 34 after fertilization |
Williams, p 30 |
| The ribs begin to form and lengthen. |
Day 35 of development |
Larsen, p 48 |
| The olfactory lobe, which is related
to the sense of smell, is present in the brain. |
Day 35 after conception |
Rugh, p 44 |
| The nasal pits deepen to form the
nasal cavity. |
Days 35-42 |
Larsen, p 230 |
| The external ears are developing. |
Days 35-49 |
Larsen, p 261 |
