BGDA Practical 7 - Week 7

From Embryology

Introduction

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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8


Key Events of Human Development during the seventh week following fertilization or clinical GA week 9.

Stage 18
Stage 18 - Right Lateral

Stage18 bf11.jpg

 ‎‎Mobile | Desktop | Original

Stage 18 | Embryo Slides
Stage 18 - Left Lateral

Stage18 bf12.jpg

 ‎‎Mobile | Desktop | Original

Stage 18 | Embryo Slides


Stage 18
Stage 19 - Left Lateral

Stage19 bf2.jpg

 ‎‎Mobile | Desktop | Original

Stage 19 | Embryo Slides
Stage 19 - Right Lateral

Stage19bf13-icon.jpg

 ‎‎Mobile | Desktop | Original

Stage 19 | Embryo Slides

Endocrine Development

Pancreas Development Week 7 to 20 pancreatic hormones secretion increases, small amount maternal insulin.

Thyng1914 fig02.jpg Stage22 pancreas a.jpg
Week 7 Week 8

Musculoskeletal Development

Musculoskeletal System Development

Limb Development

Digits - hand and foot "paddles", death (apoptosis) of cells between digits continues.

Human Digital rays (week 7) Mouse apoptosis
ME28 002.jpg Mouse interdigit apoptosis 01.jpg


  • Ossification - bones form by endochondral ossification and throughout embryo replacement of cartilage with bone (week 5 onward).
    • mesenchyme condensation -> cartilage development -> cartilage death -> vascularisation -> bone development (primary ossification)
  • endochondral ossification - (Greek, endon = within) The developmental term used to describe the process of the replacement of the embryonic body skeleton "template" formed by cartilage with bone. The osteoblasts are the bone-forming cells. The other bone formation process is intramembranous ossification.
  • intramembranous ossification - The term used to describe the process of replacement of a membranous mesenchyme with bone by osteoblasts (bone-forming cells). Mesenchymal cells (osteoprogenitor cells) differentiate into osteoblasts at the initial sites of ossification (ossification centre). Occurs in skull (jaw, cranial vault) and clavicle. The majority of the skeleton is formed by an alternative process of bone formation on a cartilaginous template, endochondral ossification.

Lip and Palate

Ventral view of head showing upper lip, maxilla and nasal region during week 7.

Stage 18
Stage18 em01.jpg Stage18 em11.jpg
Stage 19
Stage19 em01.jpg Stage19 em11.jpg

Neural

Neural System Development - meninges develop with the appearance of the dura mater.[1]


Week 7 Interactive Component

Attempt the Quiz - Week 7  
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Here are a few simple Quiz questions that relate to Week 7 (GA week 9) from the lecture and practical.







  

1

The digits of the upper and lower limbs are separated during development of the hand and foot "paddles" by the process:

  autophagy, that is a "programmed cell death"
  apoptosis, that is a "programmed cell death"
  cell migration, that separates the developing digits
  epithelial mesenchymal transition, that separates the developing digits
  mesenchymal epithelial transition, that separates the developing digits

2

Which of the following statements about cleft lip is most correct

  cleft lip is failure of the maxillary prominences to fuse with the medial nasal prominences
  cleft lip is failure of the maxillary shelves to fuse with the medial nasal prominences
  cleft lip is failure of nasal septum to fuse with the maxillary prominences
  cleft lip occurs during the early fetal period
  cleft lip occurs due to a single known teratogen

3

Bone formation by endochondral ossification:

  only occurs in the body
  replaces mesoderm with bone
  replaces mesenchyme with bone
  replaces cartilage with bone
  replaces fibrocartilage with bone

4

One cardiac process occurring during week 7 is:

  atrial septation
  atrio-ventricular septation
  ventricular septation
  heart looping
  valve formation


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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8


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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8


Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

Timeline

Week 7 - Human Embryo Stages and Events (GA week 9) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
43
Endocrine - Pancreas Development Week 7 to 20 pancreatic hormones secretion increases, small amount maternal insulin

Respiratory System Development Week 7 - enlargement of liver stops descent of heart and lungs

44
Stage 18 Stage18 bf1c.jpg

Limb Bone form by endochondrial ossification and throughout embryo replacement of cartilage with bone (week 5-12).

Smell vomeronasal fibres and nervus terminalis[2]

Liver obturation due to epithelial proliferation, bile ducts became reorganized, continuity between liver cells and gut[3]

Neural System Development duramater appears[1]

45
   

Liver (stage 18 to 23) biliary ductules developed in periportal connective tissue produces ductal plates that receive biliary capillaries[3]

46
   
47
   
48
Stage 19 Stage19 bf1c.jpg Neural System Development accessory olivary nucleus appears[4]
49
   
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. 1.0 1.1 Patelska-Banaszewska M & Woźniak W. (2004). The development of the epidural space in human embryos. Folia Morphol. (Warsz) , 63, 273-9. PMID: 15478101
  2. Müller F & O'Rahilly R. (2004). Olfactory structures in staged human embryos. Cells Tissues Organs (Print) , 178, 93-116. PMID: 15604533 DOI.
  3. 3.0 3.1 Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat and in man during the embryonic period (Carnegie stages 11-23). Microsc. Res. Tech. , 39, 314-27. PMID: 9407542 <314::AID-JEMT2>3.0.CO;2-H DOI.
  4. Müller F & O'Rahilly R. (1990). The human brain at stages 18-20, including the choroid plexuses and the amygdaloid and septal nuclei. Anat. Embryol. , 182, 285-306. PMID: 2268071


See also the 1914 Historic description of a Harvard Collection 17.8 mm Human Embryo that from external appearance is approximately a Stage 19 human embryo.


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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8