Talk:Endocrine System Development - Revision history

Z8600021 at 03:29, 1 November 2016

2016-11-01T03:29:43Z

Z8600021 at 03:06, 1 November 2016

2016-11-01T03:06:06Z

← Older revision		Revision as of 13:06, 1 November 2016
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	Stage 20		Stage 20

	* [[Endocrine - Pituitary Development‎\|Hypophysis]] - the adenohypophysial epithelium adjacent to the neurohy- pophysis constitutes the beginning pars intermedia (O'Rahilly 1973 a).		* [[Endocrine - Pituitary Development‎\|Hypophysis]] - the adenohypophysial epithelium adjacent to the neurohy- pophysis constitutes the beginning pars intermedia (O'Rahilly 1973 a). The walls of the craniopharyngeal pouch bud into the mesenchyme (Andersen et al. 1971 ; Jirfisek 1980).
	The walls of the craniopharyngeal pouch bud into the mesenchyme (~~An- dersen~~ et al. 1971 ; ~~Jir/tsek~~ 1980).
	* Thymus - the right and left components are in contact with each other (Weller 1933)but are "never completely fused" (Norris 1938, Siegler 1969). Thymic cortex appears (in stages 20-22) as a result, according to Norris		* Thymus - the right and left components are in contact with each other (Weller 1933)but are "never completely fused" (Norris 1938, Siegler 1969). Thymic cortex appears (in stages 20-22) as a result, according to Norris
	(1938), of migration of and covering by "cells derived from the cervical sinus".		(1938), of migration of and covering by "cells derived from the cervical sinus".

Z8600021 at 01:41, 1 November 2016

2016-11-01T01:41:04Z

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Z8600021 at 01:37, 1 November 2016

2016-11-01T01:37:03Z

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Z8600021 at 01:32, 1 November 2016

2016-11-01T01:32:59Z

← Older revision		Revision as of 11:32, 1 November 2016
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	{\|		{\|
	! bgcolor="~~F5FAFF”~~ \|Week		\|-bgcolor="CEDFF2"
			! width=100px\|Week
	! Carnegie Stage		! Carnegie Stage
	! [[Endocrine - Pituitary Development‎\|Pineal]] (Epiphysis)		! [[Endocrine - Pituitary Development‎\|Pineal]] (Epiphysis)

Z8600021 at 01:31, 1 November 2016

2016-11-01T01:31:38Z

← Older revision		Revision as of 11:31, 1 November 2016
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	{\|		{\|
	! bgcolor="F5FAFF”\| Week		! bgcolor="F5FAFF” \|Week
	! Carnegie Stage		! Carnegie Stage
	! [[Endocrine - Pituitary Development‎\|Pineal]] (Epiphysis)		! [[Endocrine - Pituitary Development‎\|Pineal]] (Epiphysis)

Z8600021 at 01:30, 1 November 2016

2016-11-01T01:30:03Z

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Z8600021 at 01:16, 1 November 2016

2016-11-01T01:16:53Z

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Z8600021 at 01:15, 1 November 2016

2016-11-01T01:15:30Z

← Older revision		Revision as of 11:15, 1 November 2016
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	\|		\|
	\|-		\|-
	\|		\| Week 5
	\| Stage 14		\| Stage 14
	\| [[Endocrine - Pineal Development‎\|Epiphysis]] - a slight irregularity in the surface outline of the intact head corresponds to the future pineal body (O'Rahilly et al. 1982). Thymus. Weller's (1933) "thymus" (the third pharyngeal pouch) becomes elongated.		\| [[Endocrine - Pineal Development‎\|Epiphysis]] - a slight irregularity in the surface outline of the intact head corresponds to the future pineal body (O'Rahilly et al. 1982). Thymus. Weller's (1933) "thymus" (the third pharyngeal pouch) becomes elongated.
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	Adrenal Medulla - paravertebral sympathetic ganglia increase in size as a result of cell division and the addition of nerve fibres from the rami communicantes. The ganglia contain three types of cells: MI, M2, and M3. The M3 cells are the" parasympathetic cells" of Zuckerkandl.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		Adrenal Medulla - paravertebral sympathetic ganglia increase in size as a result of cell division and the addition of nerve fibres from the rami communicantes. The ganglia contain three types of cells: MI, M2, and M3. The M3 cells are the" parasympathetic cells" of Zuckerkandl.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	\|-		\|-
	\|		\| Week 5
	\| Stage 15		\| Stage 15
	\| [[Endocrine - Pineal Development‎\|Epiphysis]] - pineal body is detectable in the roof of the diencephalon (Stadium I of Turkewitsch 1933) (O'Rahilly 1968).		\| [[Endocrine - Pineal Development‎\|Epiphysis]] - pineal body is detectable in the roof of the diencephalon (Stadium I of Turkewitsch 1933) (O'Rahilly 1968).
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	\| Adrenal Cortex - primordium is first recognizable. A new type of cell (C1) from the coelomic epithelium is found in the subjacent mesenchyme. New cells (C2) appear in the medial wall of mesonephric glomeruli and begin to migrate into the suprarenal primordium.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> Jirfisek (1980) denies a mesonephric contribution to the suprarenal. Adrenal Medulla - all types of cells (M1, M2, and M3) increase in number. From stage 15 to stage 18, the suprarenal primordium is cigar-shaped and extends from segment T6 to segment L1, lateral to the aorta and mesogastrium.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		\| Adrenal Cortex - primordium is first recognizable. A new type of cell (C1) from the coelomic epithelium is found in the subjacent mesenchyme. New cells (C2) appear in the medial wall of mesonephric glomeruli and begin to migrate into the suprarenal primordium.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> Jirfisek (1980) denies a mesonephric contribution to the suprarenal. Adrenal Medulla - all types of cells (M1, M2, and M3) increase in number. From stage 15 to stage 18, the suprarenal primordium is cigar-shaped and extends from segment T6 to segment L1, lateral to the aorta and mesogastrium.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	\|-		\|-
	\|		\| Week 6
	\| Stage 16		\| Stage 16
	\| [[Endocrine - Pineal Development‎\|Epiphysis]] - cellular migration in an external direction occurs in the pineal body during stages 16 and 17 (Stadium 2 of Turkewitsch 1933) (O'Rahilly 1968).		\| [[Endocrine - Pineal Development‎\|Epiphysis]] - cellular migration in an external direction occurs in the pineal body during stages 16 and 17 (Stadium 2 of Turkewitsch 1933) (O'Rahilly 1968).
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	\| Adrenal Cortex. Another type of cell (C3) arises from the coelomic epithe- lium. Both C1 and C3 cells enter the suprarenal primordium. An "enormous immigration" of C2 cells occurs.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> Adrenal Medulla - cells of neural origin are migrating into the gland, separating the cortical cells into islands. Nerve fibres from the ganglia ac- company the M1 and M3 cells. The M2 cells remain in the ganglia and become sympathetic ganglion cells.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		\| Adrenal Cortex. Another type of cell (C3) arises from the coelomic epithe- lium. Both C1 and C3 cells enter the suprarenal primordium. An "enormous immigration" of C2 cells occurs.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> Adrenal Medulla - cells of neural origin are migrating into the gland, separating the cortical cells into islands. Nerve fibres from the ganglia ac- company the M1 and M3 cells. The M2 cells remain in the ganglia and become sympathetic ganglion cells.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	\|-		\|-
	\|		\| Week 6
	\| Stage 17		\| Stage 17
	\|		\|
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	\| Adrenal Cortex - dorsal part of the whole suprarenal primordium is disorganized by the invasion of sympathetic nerves and cells, while the band of C2 cells and the coelomic epithelium remain intact (Crowder 1957). Adrenal Medulla - first neural migration is at its height. Growth of the para-aortic complex is extensive. The plexiform complex is derived from paravertebral sympathetic ganglia T6-12 and usually L 1. Included in it are the primordia of the suprarenal medulla and of the celiac, superior mesenteric, and renal plexuses. Nerve fibres and "paraganglion" (M3) cells enter.		\| Adrenal Cortex - dorsal part of the whole suprarenal primordium is disorganized by the invasion of sympathetic nerves and cells, while the band of C2 cells and the coelomic epithelium remain intact (Crowder 1957). Adrenal Medulla - first neural migration is at its height. Growth of the para-aortic complex is extensive. The plexiform complex is derived from paravertebral sympathetic ganglia T6-12 and usually L 1. Included in it are the primordia of the suprarenal medulla and of the celiac, superior mesenteric, and renal plexuses. Nerve fibres and "paraganglion" (M3) cells enter.
	\|-		\|-
	\|		\| Week 7
	\| Stage 18		\| Stage 18
	\| [[Endocrine - Pineal Development‎\|Epiphysis]] - cellular migration in the pineal body forms a distinct "anterior lobe" in which follicles appear (Stadium 3 of Turkewitsch 1933) (O'Rahilly 1973 a).		\| [[Endocrine - Pineal Development‎\|Epiphysis]] - cellular migration in the pineal body forms a distinct "anterior lobe" in which follicles appear (Stadium 3 of Turkewitsch 1933) (O'Rahilly 1973 a).
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	\| Adrenal Cortex - gland becomes reorganized. The C1, 2, and 3 cells form cords as sinusoids develop. Cells divide at or near the surface, where new cells are added.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		\| Adrenal Cortex - gland becomes reorganized. The C1, 2, and 3 cells form cords as sinusoids develop. Cells divide at or near the surface, where new cells are added.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	\|-		\|-
	\|		\| Week 7
	\| Stage 19		\| Stage 19
	\| [[Endocrine - Pineal Development‎\|Epiphysis]] - the "anterior lobe" of the pineal body shows a characteristic step and wedge appearance (Stadium 4 of Turkewitsch 1933) (O'Rahilly 1968).		\| [[Endocrine - Pineal Development‎\|Epiphysis]] - the "anterior lobe" of the pineal body shows a characteristic step and wedge appearance (Stadium 4 of Turkewitsch 1933) (O'Rahilly 1968).
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	\| Adrenal Cortex - C2 cells lie on the surface of the gland and form a "capsule".<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> Adrenal Medulla - Sympathicoblasts penetrate the cortex at stages 19 and 20, and form scattered islets of medullary tissue throughout the cortex (Jirfisek 1980).		\| Adrenal Cortex - C2 cells lie on the surface of the gland and form a "capsule".<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> Adrenal Medulla - Sympathicoblasts penetrate the cortex at stages 19 and 20, and form scattered islets of medullary tissue throughout the cortex (Jirfisek 1980).
	\|-		\|-
			\| Week 8
	\| Stage 20		\| Stage 20
	\|		\|
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	\|		\|
	\|-		\|-
	\|		\| Week 8
	\| Stage 21		\| Stage 21
	\|		\|
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	\| Adrenal Cortex - the cellular "capsule" becomes covered by a layer of fibrous tissue.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		\| Adrenal Cortex - the cellular "capsule" becomes covered by a layer of fibrous tissue.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	\|-		\|-
	\|		\| Week 8
	\| Stage 22		\| Stage 22
	\|		\|
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	\| Adrenal Cortex - the C2 cells have changed and resemble fibrocytes.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		\| Adrenal Cortex - the C2 cells have changed and resemble fibrocytes.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	\|-		\|-
	\|		\| Week 8
	\| Stage 23		\| Stage 23
	\| [[Endocrine - Pineal Development‎\|Epiphysis]] - The pineal body has reached Stadium 5 of Turkewitsch (1933).<ref name=O'Rahilly1968>{{Ref-O'Rahilly1968}}</ref>		\| [[Endocrine - Pineal Development‎\|Epiphysis]] - The pineal body has reached Stadium 5 of Turkewitsch (1933).<ref name=O'Rahilly1968>{{Ref-O'Rahilly1968}}</ref>

Z8600021 at 01:13, 1 November 2016

2016-11-01T01:13:41Z

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← Older revision		Revision as of 13:29, 1 November 2016
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	* [[Endocrine - Pituitary Development‎\|Hypophysis]] - basement membranes of the craniopharyngeal pouch and the brain are clearly in contact (O'Rahilly 1973).		* [[Endocrine - Pituitary Development‎\|Hypophysis]] - basement membranes of the craniopharyngeal pouch and the brain are clearly in contact (O'Rahilly 1973).
	* Thymus - Weller (1933) recognized already a thymic primordium "of considerable size" on the ventral part of the third pharyngeal pouch, whereas Norris (1938) considered this stage to be "preprimordial"		* Thymus - Weller (1933)<ref name=Weller1933>{{Ref-Weller1933}}</ref> recognized already a thymic primordium "of considerable size" on the ventral part of the third pharyngeal pouch, whereas Norris (1938) considered this stage to be "preprimordial"
	* [[Endocrine - Thyroid Development‎\|Thyroid]] - median thyroid is now bilobed and is connected to the pharynx by a hollow pedicle ~~(Weller 1933)~~. The telopharyngeal body has been regarded as a "lateral thyroid component" by some workers ~~(e.g. Weller 1933)~~.		* [[Endocrine - Thyroid Development‎\|Thyroid]] - median thyroid is now bilobed and is connected to the pharynx by a hollow pedicle.<ref name=Weller1933>{{Ref-Weller1933}}</ref> The telopharyngeal body has been regarded as a "lateral thyroid component" by some workers.<ref name=Weller1933>{{Ref-Weller1933}}</ref>
	* Pancreas - ventral pancreas may perhaps be distinguishable (Politzer 1952).		* Pancreas - ventral pancreas may perhaps be distinguishable (Politzer 1952).

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	* [[Endocrine - Pituitary Development‎\|Hypophysis]] - craniopharyngeal pouch is prominent (Streeter 1945) and the notochord appears to be inserted into its dorsal wall. The craniopharyngeal pouch has become elongated and blood vessels are beginning to grow in between the basement membranes of the pouch and brain (O'Rahilly 1973a).		* [[Endocrine - Pituitary Development‎\|Hypophysis]] - craniopharyngeal pouch is prominent (Streeter 1945) and the notochord appears to be inserted into its dorsal wall. The craniopharyngeal pouch has become elongated and blood vessels are beginning to grow in between the basement membranes of the pouch and brain (O'Rahilly 1973a).
	* [[Endocrine - Pineal Development‎\|Epiphysis]] - a slight irregularity in the surface outline of the intact head corresponds to the future pineal body (O'Rahilly et al. 1982). Thymus. Weller's (1933) "thymus" (the third pharyngeal pouch) becomes elongated.		* [[Endocrine - Pineal Development‎\|Epiphysis]] - a slight irregularity in the surface outline of the intact head corresponds to the future pineal body (O'Rahilly et al. 1982). Thymus. Weller's (1933)<ref name=Weller1933>{{Ref-Weller1933}}</ref> "thymus" (the third pharyngeal pouch) becomes elongated.
	* [[Endocrine - Parathyroid Development\|Parathyroids]] - "Parathyrogenic zones" (Politzer and Hann 1935) are recognizable (Streeter 1945). The parathyroid 4 primordium has been illustrated at this stage by Weller (1933, Fig. 16).		* [[Endocrine - Parathyroid Development\|Parathyroids]] - "Parathyrogenic zones" (Politzer and Hann 1935) are recognizable (Streeter 1945). The parathyroid 4 primordium has been illustrated at this stage by Weller (1933, Fig. 16).
	* [[Endocrine - Thyroid Development‎\|Thyroid]] - thyroid pedicle shows further elongation but is still connected to the epithelium of the pharynx ~~(Weller 1933)~~. Right and left lobes and an isthmus may perhaps be presaged (ibid.).		* [[Endocrine - Thyroid Development‎\|Thyroid]] - thyroid pedicle shows further elongation but is still connected to the epithelium of the pharynx.<ref name=Weller1933>{{Ref-Weller1933}}</ref> Right and left lobes and an isthmus may perhaps be presaged (ibid.).
	* Adrenal Cortex - A change in the characteristics of the cells of the coelomic epithelium appears between the mesogastrium and the lateral end of the mesonephros.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		* Adrenal Cortex - A change in the characteristics of the cells of the coelomic epithelium appears between the mesogastrium and the lateral end of the mesonephros.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	* Adrenal Medulla - paravertebral sympathetic ganglia increase in size as a result of cell division and the addition of nerve fibres from the rami communicantes. The ganglia contain three types of cells: MI, M2, and M3. The M3 cells are the" parasympathetic cells" of Zuckerkandl.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		* Adrenal Medulla - paravertebral sympathetic ganglia increase in size as a result of cell division and the addition of nerve fibres from the rami communicantes. The ganglia contain three types of cells: MI, M2, and M3. The M3 cells are the" parasympathetic cells" of Zuckerkandl.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
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	* Thymus - according to Norris (1938), "not until the primordium of the parathyroid [3] has been outlined can the remaining portion of the third pouch be recognized, by exclusion, as the primordium of the endodermal thymus".		* Thymus - according to Norris (1938), "not until the primordium of the parathyroid [3] has been outlined can the remaining portion of the third pouch be recognized, by exclusion, as the primordium of the endodermal thymus".
	* [[Endocrine - Parathyroid Development\|Parathyroids]] - parathyrogenic zones are closely related to the third and fourth aortic arches at 9 mm (Politzer and Hann 1935, unstaged embryo). Parathyroid 3 is identifiable on the anterior wall of the third pharyngeal pouch (Weller 1933, Fig. 17) and "does not arise from a dorsal lobule" of the pouch (Norris 1937). The "sudden appearance of well-differentiated clear chief cells in the early primordia of the parathyroids" at 9 mm was emphasized by Norris (1937).		* [[Endocrine - Parathyroid Development\|Parathyroids]] - parathyrogenic zones are closely related to the third and fourth aortic arches at 9 mm (Politzer and Hann 1935, unstaged embryo). Parathyroid 3 is identifiable on the anterior wall of the third pharyngeal pouch (Weller 1933, Fig. 17) and "does not arise from a dorsal lobule" of the pouch (Norris 1937). The "sudden appearance of well-differentiated clear chief cells in the early primordia of the parathyroids" at 9 mm was emphasized by Norris (1937).
	* [[Endocrine - Thyroid Development‎\|Thyroid]] - has lost its continuity with the pharynx and it consists of two lobes, an isthmus, and a remnant of the pedicle ~~(Weller 1933)~~.		* [[Endocrine - Thyroid Development‎\|Thyroid]] - has lost its continuity with the pharynx and it consists of two lobes, an isthmus, and a remnant of the pedicle.<ref name=Weller1933>{{Ref-Weller1933}}</ref>
	* Adrenal Cortex. Another type of cell (C3) arises from the coelomic epithe- lium. Both C1 and C3 cells enter the suprarenal primordium. An "enormous immigration" of C2 cells occurs.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		* Adrenal Cortex. Another type of cell (C3) arises from the coelomic epithe- lium. Both C1 and C3 cells enter the suprarenal primordium. An "enormous immigration" of C2 cells occurs.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
	* Adrenal Medulla - cells of neural origin are migrating into the gland, separating the cortical cells into islands. Nerve fibres from the ganglia ac- company the M1 and M3 cells. The M2 cells remain in the ganglia and become sympathetic ganglion cells.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		* Adrenal Medulla - cells of neural origin are migrating into the gland, separating the cortical cells into islands. Nerve fibres from the ganglia ac- company the M1 and M3 cells. The M2 cells remain in the ganglia and become sympathetic ganglion cells.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
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	* [[Endocrine - Pituitary Development‎\|Hypophysis]] - juxtacerebral wall of the craniopharyngeal pouch is the thicker. The lateral lobes (future infundibular, or tuberal, part) and the anterior chamber (Vorraum) are clearly visible (O'Rahilly 1973 a). The infundibular recess displays a characteristically folded wall, namely the neurohypophysis (O'Rahilly 1973 a).		* [[Endocrine - Pituitary Development‎\|Hypophysis]] - juxtacerebral wall of the craniopharyngeal pouch is the thicker. The lateral lobes (future infundibular, or tuberal, part) and the anterior chamber (Vorraum) are clearly visible (O'Rahilly 1973 a). The infundibular recess displays a characteristically folded wall, namely the neurohypophysis (O'Rahilly 1973 a).
	* Thymus - connection of the thymus with the pharynx has been severed (Weller 1933). The thymus is intimately approximated to the cervical duct (ibid.) According to Norris (1937), both third and fourth pouches make contact with the ectoderm, although only the third "receives an increment from the ectoderm".		* Thymus - connection of the thymus with the pharynx has been severed (Weller 1933). The thymus is intimately approximated to the cervical duct (ibid.) According to Norris (1937), both third and fourth pouches make contact with the ectoderm, although only the third "receives an increment from the ectoderm".
	* [[Endocrine - Parathyroid Development\|Parathyroids]] -parathyroid 4 is attached to the lateral surface of what Weller (1933) termed the "lateral thyroid component"		* [[Endocrine - Parathyroid Development\|Parathyroids]] -parathyroid 4 is attached to the lateral surface of what Weller (1933)<ref name=Weller1933>{{Ref-Weller1933}}</ref> termed the "lateral thyroid component"
	* [[Endocrine - Thyroid Development‎\|Thyroid]]. The lobes of the thyroid curve around the carotid arteries and are connected by a delicate isthmus. Lacunae "should not be confused with lumina of follicles" ~~(Weller 1933)~~.		* [[Endocrine - Thyroid Development‎\|Thyroid]]. The lobes of the thyroid curve around the carotid arteries and are connected by a delicate isthmus. Lacunae "should not be confused with lumina of follicles".<ref name=Weller1933>{{Ref-Weller1933}}</ref>
	* Adrenal Cortex - dorsal part of the whole suprarenal primordium is disorganized by the invasion of sympathetic nerves and cells, while the band of C2 cells and the coelomic epithelium remain intact (Crowder 1957).		* Adrenal Cortex - dorsal part of the whole suprarenal primordium is disorganized by the invasion of sympathetic nerves and cells, while the band of C2 cells and the coelomic epithelium remain intact (Crowder 1957).
	* Adrenal Medulla - first neural migration is at its height. Growth of the para-aortic complex is extensive. The plexiform complex is derived from paravertebral sympathetic ganglia T6-12 and usually L 1. Included in it are the primordia of the suprarenal medulla and of the celiac, superior mesenteric, and renal plexuses. Nerve fibres and "paraganglion" (M3) cells enter.		* Adrenal Medulla - first neural migration is at its height. Growth of the para-aortic complex is extensive. The plexiform complex is derived from paravertebral sympathetic ganglia T6-12 and usually L 1. Included in it are the primordia of the suprarenal medulla and of the celiac, superior mesenteric, and renal plexuses. Nerve fibres and "paraganglion" (M3) cells enter.
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	* [[Endocrine - Pineal Development‎\|Epiphysis]] - cellular migration in the pineal body forms a distinct "anterior lobe" in which follicles appear (Stadium 3 of Turkewitsch 1933) (O'Rahilly 1973 a).		* [[Endocrine - Pineal Development‎\|Epiphysis]] - cellular migration in the pineal body forms a distinct "anterior lobe" in which follicles appear (Stadium 3 of Turkewitsch 1933) (O'Rahilly 1973 a).
	* Thymus- thymus makes contact with the thyroid gland and contains a series of canals internally (Weller 1933).		* Thymus- thymus makes contact with the thyroid gland and contains a series of canals internally (Weller 1933).
	* [[Endocrine - Thyroid Development‎\|Thyroid]] - median thyroid is in contact with "lateral thyroid ~~compo~~- ~~nents" (Weller 1933)~~ but others have maintained that the telopharyngeal body should not be regarded as a thyroid component (Bejdl and Politzer 1953). The lobes of the thyroid are "composed of series of continuously communicating solid annectent bars" ~~(Weller 1933). This~~ is "the earliest stage of the definitive thyroid" ~~(ibid.)~~. First differentiation occurs in Weller's (1933) "lateral thyroid component," which is beginning to "blend into uniformly constituted thyroid tissue". Weller (1933) illustrated (Fig. 11) a thyroid gland that still showed continuity between its pedicle and the epithelium of the pharynx.		* [[Endocrine - Thyroid Development‎\|Thyroid]] - median thyroid is in contact with "lateral thyroid components"<ref name=Weller1933>{{Ref-Weller1933}}</ref>but others have maintained that the telopharyngeal body should not be regarded as a thyroid component (Bejdl and Politzer 1953). The lobes of the thyroid are "composed of series of continuously communicating solid annectent bars" this is "the earliest stage of the definitive thyroid".<ref name=Weller1933>{{Ref-Weller1933}}</ref> First differentiation occurs in Weller's (1933) "lateral thyroid component," which is beginning to "blend into uniformly constituted thyroid tissue". Weller (1933) illustrated (Fig. 11) a thyroid gland that still showed continuity between its pedicle and the epithelium of the pharynx.
	* Adrenal Cortex - gland becomes reorganized. The C1, 2, and 3 cells form cords as sinusoids develop. Cells divide at or near the surface, where new cells are added.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>		* Adrenal Cortex - gland becomes reorganized. The C1, 2, and 3 cells form cords as sinusoids develop. Cells divide at or near the surface, where new cells are added.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>

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	* [[Endocrine - Pituitary Development‎\|Hypophysis]] - the adenohypophysial epithelium adjacent to the neurohy- pophysis constitutes the beginning pars intermedia (O'Rahilly 1973 a). The walls of the craniopharyngeal pouch bud into the mesenchyme (Andersen et al. 1971 ; Jirfisek 1980).		* [[Endocrine - Pituitary Development‎\|Hypophysis]] - the adenohypophysial epithelium adjacent to the neurohy- pophysis constitutes the beginning pars intermedia (O'Rahilly 1973 a). The walls of the craniopharyngeal pouch bud into the mesenchyme (Andersen et al. 1971 ; Jirfisek 1980).
	* Thymus - the right and left components are in contact with each other ~~(Weller 1933)~~but are "never completely fused" (Norris 1938, Siegler 1969). Thymic cortex appears (in stages 20-22) as a result, according to Norris		* Thymus - the right and left components are in contact with each other<ref name=Weller1933>{{Ref-Weller1933}}</ref> but are "never completely fused" (Norris 1938, Siegler 1969). Thymic cortex appears (in stages 20-22) as a result, according to Norris
	(1938), of migration of and covering by "cells derived from the cervical sinus".		(1938), of migration of and covering by "cells derived from the cervical sinus".
	* [[Endocrine - Parathyroid Development\|Parathyroids]] - the parathyroid glands are attached to the lateral lobes of the thyroid (Weller 1933).		* [[Endocrine - Parathyroid Development\|Parathyroids]] - the parathyroid glands are attached to the lateral lobes of the thyroid (Weller 1933).
	Weller (1933, Fig. 23) showed parathyroid 3 still rostral to parathyroid 4 at 23 mm, whereas (presumably due to variation in the "descent" of the thymus) Norris (1937, Fig. 4) showed parathyroid 3 rostral to, level with, and caudal to parathyroid 4 in embryos of 16-17 mm.		Weller (1933, Fig. 23) showed parathyroid 3 still rostral to parathyroid 4 at 23 mm, whereas (presumably due to variation in the "descent" of the thymus) Norris (1937, Fig. 4) showed parathyroid 3 rostral to, level with, and caudal to parathyroid 4 in embryos of 16-17 mm.
	* [[Endocrine - Thyroid Development‎\|Thyroid]] - the "annectent bars" of the thyroid are more compact then previously ~~(Weller 1933)~~. The thyroid now exhibits its definitive external form.		* [[Endocrine - Thyroid Development‎\|Thyroid]] - the "annectent bars" of the thyroid are more compact then previously.<ref name=Weller1933>{{Ref-Weller1933}}</ref> The thyroid now exhibits its definitive external form.

	Stage 21		Stage 21