embryology details In a very good way explanation

embryology details In a very good way explanation

1. B y Mumuksha Modi Guided by Dr Nikita Patel Embryology

2. Introduction Processes and regulations in the prenatal growth and development of an organism/individual in the female genital tract. It begins with the fusion of male and female gametes (fertilization) in the fallopian tube up to the birth as a neonate.

3. Diploid Haploid Double number The number of chromosomes in each cell is fixed for a given species and in human beings, it is 46. Half number In spermatozoa and ova, the number of chromosomes is only half the diploid number, i.e. 23. Chromosomes

4. “After fertilization, the resulting zygote has 23 chromosomes from the sperm (or father), and 23 from the ovum (or mother). The diploid number is thus restored”

5. The 46 chromosomes in each cell can be divided into 44 autosomes and 2 sex chromosomes. The sex chromosomes may be of two kinds, X or Y

6. The daughter cells must have chromosomes identical in number (and in genetic content) to those in the mother cell. This type of cell division is called mitosis. Mitosis

7. A different kind of cell division called meiosis occurs during the formation of the gametes. This consists of two successive divisions called the first and second meiotic divisions. The cells resulting from these divisions (i.e. gametes) differ from other cells of the body in that – the number of chromosomes is reduced to half the normal number. Meiosis

8. The cells of the inner cell mass multiply ↓ form an embryonic disc having two layers Epiblast ( Cells aka pluripotent ) Hypoblast 3 germ layers Ectoderm (outer) Endoderm (inner) Mesoderm (middle) Cells → flattened and line the yolk sac Cavity appears Amniotic cavity Cavity appears Yolk sac DURING 2 ND WEEK OF DEVELOPMENT

9. Prosencephalon Mesencephalon Rhombencephalon Diencephalon Telencephalon Midbrain Metencephalon Myelencephalon Pons and cerebellum Medulla oblongata

10. Effect of recession of spinal cord on course of spinal nerves. (A) Shows the condition before recession begins. Spinal nerves pass horizontally from the spinal cord to their exit from the vertebral canal; (B) Shows the condition after recession has occurred. The nerves now have to run obliquely downwards to reach the points of exit. The obliquity is greatest in the case of the lowest nerves

11. Anomalies of brain and spinal cord Neural tube defects ( ntds ) Due to non-approximation of neural folds, they result in an opening in the spinal cord or brain or both from the early human development ANOMALIES

12. Open NTDs Closed NTDs more common. It results when the brain and/or spinal cord are exposed at birth through a defect in the skull or vertebrae. Examples are anencephaly and spina bifida rare It occurs when the spinal defect is covered by skin. It is due to malformation of fat/bone/membranes

13. Outward bulging of neural tube and covering membranes Anencephaly and spina bifida Myelocele Rachischisis due to non-closure of the neural tube, the nervous tissue is exposed on the surface. Failure of closure of anterior (anencephaly) and posterior (spina bifida) neuropore When this happens in the region of the brain Failure of closure of entire neural tube results in a condition As a result of non-fusion of the neural tube, or of overlying bones (e.g. spina bifida), neural tissue may lie outside the cranial cavity or vertebral canal.

14. Encephalocele Myelocele Anencephaly Rachischisis

15. Hydrocephalus Due to blockage to the circulation of CSF or its excessive production. ANOMALIES

16. Due to accumulation of abnormal quantity of cerebrospinal fluid (CSF) in the ventricular system of brain. The pressure of the fluid causes degeneration of nervous tissue. The ventricles become very large and the infant is born with a large head.

17. Syringomyelia Dandy-Walker syndrome The enlargement of central canal and associated abnormal cavities near central canal A form of hydrocephalus resulting from blockage of median and lateral apertures of the fourth ventricle. Enlargement is predominantly in the posterior cranial fossa and the cerebellum is abnormal.

18. Summary

19. Thank you!!