Structures formed during the third week of development of IUL.
Brief account on those structures formed in second and third week of IUL. 2057
Development of adrenal, thyroid and pituitary glands
Mention briefly the genetic cause of downs syndrome? 2068/5
Formation of germ layers? [TU]
The cells from the epiblast migrate down through the primitive streak to the site of hypoblast. The cells of hypoblast degenerate and are replaced by the migrated cells to form endoderm.
The cells of epiblast that migrate and remain in the position between epiblast and hypoblast form middle layer. The cells that migrate either in left or right side to form mesoderm.
The remaining cells in epiblast form ectoderm.
Derivatives of germ layers? [TU]
What are the sub-divisions of ectoderm?
- o Neuroectoderm – occupy midline
- o Neural crest ectoderm – occupy side of neuroectoderm cells
- o Surface ectoderm
Derivatives of surface ectoderm. [TU 2054]
We have 5 senses. So the derivatives of surface ectoderm are according to that
1. Touch: Epidermis, nail, hair
2. Vision: lens
3. Smell: olfactory epithelium
4. Taste: Oral Cavity Epithelium
5. Hearing: sensory organs of ear
Finally we also have 3 Glands - Salivary gland, Sweat Gland and Mammary Gland!
Last but not the Least Adenohypophysis
Neural crest and derivatives.
- o Melanocytes, Meninges - Pia and arachnoid
- o Odontoblast
- o Tracheal cartilage
- o Endocardial cushion
- o Laryngeal cartilage/Leptomeninges
- o Pseudounipolar cells / Postganglionic neurons.
- o Adrenal Medulla
- o Schwann cells
- o Spiral Membrane
- o Dorsal root ganglia
- o Parafollicular C cells of the thyroid / craniofacial structures. (skull)
[@ MOTEL PASS DC
Derivatives of Neuroectoderm?
- C NS: Somatic Motor Neurons and Preganglionic Neurons (ANS)
- A strocytes ☆
- N eurohypophysis (Posterior Pituitary)
- P ineal gland
- R etina & O ptic Nerve
- O ligodendrocytes (myelinate all the cell
[@ CAN PRO]
Derivative of neural tube?
Brain and spinal cord
Short note on Umbilical cord? [TU 2057]
Short note on yolk sac. [TU 2057]
The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast adjacent to the embryonic disk.
The yolk sac is important in early embryonic blood supply, and much of it is incorporated into the primordial gut during the fourth week of development.
- Primary yolk sac: it is the vesicle which develops in the second week, its floor is represented by Heuser's membrane and its ceiling by the hypoblast. It is also known as the exocoelomic cavity.
- Secondary yolk sac: this structure is formed when the extraembryonic mesoderm separates to form the extraembryonic coelom; cells from the mesoderm pinch off an area of the yolk sac, and what remains is the secondary yolk sac.
- The final yolk sac: during the fourth week of development, during organogenesis, part of the yolk sac is surrounded by endoderm and incorporated into the embryo as the gut. The remaining part of the yolk sac is the final yolk sac.
Short note on placenta and amnion. [TU 2057]
Short note on Notochord. [TU 2056,57]