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| ! width=50px|Week | | ! Carnegie Stage |
| ! width=50px|Carnegie Stage | | ! Stage 13 |
| ! width=250px|[[Endocrine - Pituitary Development|Pineal]] (Epiphysis) | | ! Stage 14 |
| ! width=250px|[[Endocrine - Pituitary Development|Pituitary]] (Hypophysis) | | ! Stage 15 |
| ! width=250px|[[Endocrine - Thyroid Development|Thyroid]] | | ! Stage 16 |
| ! width=250px|[[Endocrine - Parathyroid Development|Parathyroid]] | | ! Stage 17 |
| ! width=250px|[[Endocrine - Thymus Development|Thymus]] | | ! Stage 18 |
| ! width=250px|[[Endocrine - Pancreas Development|Pancreas]] | | ! Stage 19 |
| ! width=250px|Adrenal (Suprarenal) Cortex/Medulla | | ! Stage 20 |
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| | ! Stage 21 |
| | bgcolor="F5FAFF" valign=top|Week 4
| | ! Stage 22 |
| | valign=top|Stage 13
| | ! Stage 23 |
| | bgcolor="F5FAFF" valign=top|
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| | valign=top|basement membranes of the craniopharyngeal pouch and the brain are clearly in contact (O'Rahilly 1973).
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| | bgcolor="F5FAFF" valign=top|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).
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| | bgcolor="F5FAFF" valign=top|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"
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| | valign=top|ventral pancreas may perhaps be distinguishable (Politzer 1952).
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| | bgcolor="F5FAFF" valign=top|Week 5
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| | valign=top| [[Carnegie stage 14|stage 14]]
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| | bgcolor="F5FAFF" valign=top| 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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| | valign=top| 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).
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| | bgcolor="F5FAFF" valign=top| 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.).
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| | valign=top| "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).
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| | valign=top| ventral pancreas (which may perhaps be distinguishable as early as stage 13) appears as an evagination from the bile duct at stages 14 (Blechschmidt 1973) and 15 (Streeter 1948). It is generally described as unpaired but, at least in some cases, may perhaps be bilobed<ref name=Odgers1930>{{Ref-Odgers1930}}</ref> or even multiple (Delmas 1939).
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| | bgcolor="F5FAFF" valign=top|'''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> '''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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| | bgcolor="F5FAFF" valign=top|Week 5
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| | valign=top| [[Carnegie stage 15|stage 15]]
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| | bgcolor="F5FAFF" valign=top|pineal body is detectable in the roof of the diencephalon (Stadium I of Turkewitsch 1933) (O'Rahilly 1968).
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| | bgcolor="F5FAFF" valign=top|thyroid primordium may be detached from the pharyngeal epithelium in some instances. "At about the time" when the thyroglossal duct "becomes broken it loses its lumen" (Grosser 1912).
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| | bgcolor="F5FAFF" valign=top|'''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. '''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>
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| | bgcolor="F5FAFF" valign=top|Week 6
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| | valign=top| [[Carnegie stage 16|stage 16]]
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| | bgcolor="F5FAFF" valign=top|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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| | valign=top|slight indication of the infundibular recess may be seen in some embryos (O'Rahilly 1973 a).
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| | bgcolor="F5FAFF" valign=top|has lost its continuity with the pharynx and it consists of two lobes, an isthmus, and a remnant of the pedicle (Weller 1933).
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| | valign=top| 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).
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| | bgcolor="F5FAFF" valign=top| 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".
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| | valign=top| dorsal pancreas and the ventral pancreas are contiguous.<ref name=Blechschmidt1973>{{Ref-Blechschmidt1973}}</ref>
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| | bgcolor="F5FAFF" valign=top| 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> 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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| | bgcolor="F5FAFF" valign=top|Week 6
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| | valign=top| [[Carnegie stage 17|stage 17]]
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| | bgcolor="F5FAFF" |
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| | valign=top| 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).
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| | bgcolor="F5FAFF" valign=top| 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).
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| | valign=top| parathyroid 4 is attached to the lateral surface of what Weller (1933) termed the "lateral thyroid component"
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| | bgcolor="F5FAFF" valign=top| 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".
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| | valign=top| ventral pancreas has now fused with dorsal (Streeter 1948). Perhaps the ventral and dorsal ducts have begun to blend (Russu and Vaida 1959).
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| | bgcolor="F5FAFF" valign=top| '''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). '''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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| | bgcolor="F5FAFF" valign=top|Week 7
| | | [[Endocrine - Pituitary Development|Pituitary]] (Hypophysis) |
| | valign=top| [[Carnegie stage 18|stage 18]]
| | | basement membranes of the craniopharyngeal pouch and the brain are clearly in contact (O'Rahilly 1973). |
| | bgcolor="F5FAFF" valign=top| cellular migration in the pineal body forms a distinct "anterior lobe" in which follicles appear (Stadium 3 of Turkewitsch 1933) (O'Rahilly 1973 a). | | | 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. |
| | valign=top| median thyroid is in contact with "lateral thyroid components" (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. | | | pineal body is detectable in the roof of the diencephalon (Stadium I of Turkewitsch 1933) (O'Rahilly 1968). |
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| | | 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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| | bgcolor="F5FAFF" valign=top| thymus makes contact with the thyroid gland and contains a series of canals internally (Weller 1933). | | | cellular migration in the pineal body forms a distinct "anterior lobe" in which follicles appear (Stadium 3 of Turkewitsch 1933) (O'Rahilly 1973 a). |
| | | | | the "anterior lobe" of the pineal body shows a characteristic step and wedge appearance (Stadium 4 of Turkewitsch 1933) (O'Rahilly 1968). |
| | bgcolor="F5FAFF" valign=top| '''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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| | bgcolor="F5FAFF" valign=top|Week 7
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| | valign=top| [[Carnegie stage 19|stage 19]]
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| | bgcolor="F5FAFF" valign=top| "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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| | valign=top| caudal part of the craniopharyngeal pouch is reduced to a closed epithelial stem (Andersen et al. 1971).
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| | bgcolor="F5FAFF" |
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| | valign=top| parathyroid 3 become detached from the pharyngeal endoderm (Jirfisek 1980).
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| | bgcolor="F5FAFF" |
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| | bgcolor="F5FAFF" valign=top| '''Cortex''' - C2 cells lie on the surface of the gland and form a "capsule".<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> '''Medulla''' - Sympathicoblasts penetrate the cortex at stages 19 and 20, and form scattered islets of medullary tissue throughout the cortex (Jirfisek 1980).
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| | bgcolor="F5FAFF" valign=top|Week 8
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| | valign=top| [[Carnegie stage 20|stage 20]]
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| | bgcolor="F5FAFF" |
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| | valign=top| adenohypophysial epithelium adjacent to the neurohy- pophysis constitutes the beginning pars intermedia (O'Rahilly 1973 a).
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| The walls of the craniopharyngeal pouch bud into the mesenchyme (An- dersen et al. 1971 ; Jir/tsek 1980).
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| | bgcolor="F5FAFF" valign=top| "annectent bars" of the thyroid are more compact then previously (Weller 1933). The thyroid now exhibits its definitive external form.
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| | valign=top| 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.
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| | bgcolor="F5FAFF" valign=top| 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".
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| | bgcolor="F5FAFF" valign=top|Week 8
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| | valign=top| [[Carnegie stage 21|stage 21]]
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| | valign=top| pharyngeal stalk becomes fragmented (Jirfisek 1980).
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| | bgcolor="F5FAFF" valign=top| '''Cortex''' - the cellular "capsule" becomes covered by a layer of fibrous tissue.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
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| | bgcolor="F5FAFF" valign=top|Week 8
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| | valign=top| [[Carnegie stage 22|stage 22]]
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| | bgcolor="F5FAFF" | | | | The pineal body has reached Stadium 5 of Turkewitsch (1933).<ref name=O'Rahilly1968>{{Ref-O'Rahilly1968}}</ref> |
| | valign=top| Parathyroids 4 become detached from the pharyngeal endoderm (Jirfisek 1980).
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| | bgcolor="F5FAFF" valign=top| Cortex - the C2 cells have changed and resemble fibrocytes.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
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| | bgcolor="F5FAFF" valign=top|Week 8
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| | valign=top| [[Carnegie stage 23|stage 23]]
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| | bgcolor="F5FAFF" valign=top| pineal body has reached Stadium 5 of Turkewitsch (1933).<ref name=O'Rahilly1968>{{Ref-O'Rahilly1968}}</ref>
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| | valign=top| adenohypophysis loss of the stalk and lobules of epithelium project into the mesodermal component of the gland, and oriented epithelial follicles are present (Streeter, 1951, plate 2). Abundant angioblasts and capillaries are found.
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| | bgcolor="F5FAFF" valign=top| cortex is well-developed, "true lobulation" has begun with the appearance of" fine superficial scallops," lymphocytes are present sparsely in the subcortical zone, and vessels are found within the thymus (Norris 1938).
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| | bgcolor="F5FAFF" valign=top| '''Cortex''' - It appears that C2 cells first enter the body of the gland at this stage. The pattern of the arterial supply is established. The cellular "capsule" is penetrated by arterial capillaries which join the sinusoids. Their points of entry give the surface of the gland an appearance of cobblestones. The zona glomerulosa is formed of CI and C3 cells. Cells from this zone and from the "capsule" migrate centrally into the cords.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref> '''Medulla''' - Nerve fibres and neuroblasts are first seen in the body of the gland. The paragangtion (M3) cells are beginning to multiply rapidly and, from 30 mm (stage 23) until birth, some are differentiating into chromaffin cells.<ref name=Crowder1957>{{Ref-Crowder1957}}</ref>
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