ANAT2341 Lab 12 - Embryo to Fetus

From Embryology
Lab 12: Introduction | Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities | Online Assessment


  • Week 8 Stage 22 and 23
  • Selected Stage 22 cross-sections and animations
  • Week 10 Fetus

Week 8 Stage 22

Stage22 bf1c.jpg
Week 8, 54 - 56 days, 23 - 28 mm

Mesoderm: heart prominence, ossification continues

Head: nose, eye, external acoustic meatus

Body:straightening of trunk, heart, liver, umbilicus: placental cord, midgut herniation, allantois, vitelline duct

Limb: upper limbs longer and bent at elbow, foot plate with webbed digits, wrist, hand plate with separated digits

Straightening of trunk, pigmented eye, eyelid, nose, external acoustic meatus, ear auricle, scalp vascular plexus, separated digits (fingers), thigh, ankle, umbilical cord

Embryo Anatomy

Now examine selected regions of the Stage 22 embryo and their overall development in the 3D animations.

Stage22-GIT-icon.jpg Stage22-CVS-icon.jpg Stage22-CNS-icon.jpg Stage22-UG-icon.jpg Stage22-SK-icon.jpg
Gastrointestinal Cardiovascular Central Nervous Urogenital Skeletal
Links: 3D reconstruction animations | embryo slices

Week 8 Stage 23

Stage23 bf1c.jpg
Week 8, 56 - 60 days, 27 - 31 mm

scalp vascular plexus, eylid, eye, nose, auricle of external ear, mouth, sholder, arm, elbow, wrist, toes separated, sole of foot, umbilical cord

Mesoderm: ossification continues

Head: eyelids, external ears, rounded head

Body: straightening of trunk, intestines herniated at umbilicus

Limbs: hands and feet turned inward

Week 10 Fetus (40mm)

Size comparison embryo-fetus actual.jpg This is an image of the actual size comparison shown in the introduction of the Embryonic stage 13, 23 and Fetal stage 10 week 40mm. This stage of development is after the embryonic period (up to week 8), but only 2 weeks into early fetal development.
Size comparison embryo-fetus.jpg The fetal period is a time of extensive growth in size and mass as well as differentiation of organ systems established in the embryonic period. In particular, the brain continues to grow and develop, the respiratory system differentiates, the urogenital system further differentiates between male/female, endocrine and gastrointestinal tract begins to function.

Compare this 10 week fetus with the earlier Carnegie stage embryos: size, head/body proportions, brain, head, skeletal development.

Note that in the early fetus the midgut remains herniated and will only be taken into the peritoneal cavity on further body wall growth.

There are 4 sections taken in the sagittal plane (moving from the right at Plane A towards the midline at Plane D). Click on the small images (or the text below) to open the linked large image pages.

Fetal 10wk urogenital 3.jpg

Midgut Herniation

Lab 12: Introduction | Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities | Online Assessment

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, May 24) Embryology ANAT2341 Lab 12 - Embryo to Fetus. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G