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* '''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. | |||
Revision as of 09:56, 19 May 2014
Introduction
Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 |
Key Events of Human Development during the seventh week (week 7) following fertilization or clinical week 9 (GA week 9).
(Place 7 week ultrasounds here)
Endocrine Development
Pancreas Development Week 7 to 20 pancreatic hormones secretion increases, small amount maternal insulin.
Week 7 | Week 8 |
Musculoskeletal Development
Musculoskeletal System Development
Limb Development
- Digits - hand and foot "paddles", death (apoptosis) of cells between digits commences.
- Ossification - bones form by endochondral ossification and throughout embryo replacement of cartilage with bone (week 5 onward).
- 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.
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. |
Detailed Week by Week
The following information is a detailed timeline of embryonic development between week 3 to 8 and content does not form part of the current practical class.
Embryo Stages and Events
Day | Stage | Event |
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 | ||
Stage 18 |
Limb Bone form by endochondrial ossification and throughout embryo replacement of cartilage with bone (week 5-12). Smell vomeronasal fibres and nervus terminalis PMID 15604533 Liver obturation due to epithelial proliferation, bile ducts became reorganized, continuity between liver cells and gut PMID 9407542 Neural System Development duramater appears PMID 15478101 | |
Liver (stage 18 to 23) biliary ductules developed in periportal connective tissue produces ductal plates that receive biliary capillaries PMID 9407542 | ||
Stage 19 | Neural System Development accessory olivary nucleus appears PMID 2268071 | |
See also the 1914 Historic description of a 17.8 mm Human Embryo that from external appearance is approximately a Stage 19 human embryo.
1914 Human Embryo 17.8 mm Harvard Collection
Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 |