GAMETOGENESIS (2) (1) PDF

General Embryology Dr. Yousif Osman Yousif GAMETOGENESIS Dr. Yousif Osman Yousif Osman Anatomy Department Dr. Yousif Osman Yousif Introduction Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif ‫ﻴﻦ)( ُﺛﻢ َﺠ َﻌ ْﻟ َﻨ ُﺎﻩ ُﻧ ْﻄ َﻔ ًﺔ ِﻓﻲ َﻘﺮ ٍارَ‬ ‫ٍ‬...

General Embryology Dr. Yousif Osman Yousif GAMETOGENESIS Dr. Yousif Osman Yousif Osman Anatomy Department Dr. Yousif Osman Yousif Introduction Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif ‫ﻴﻦ)( ُﺛﻢ َﺠ َﻌ ْﻟ َﻨ ُﺎﻩ ُﻧ ْﻄ َﻔ ًﺔ ِﻓﻲ َﻘﺮ ٍارَ‬ ‫ٍ‬ ‫ْ‬ ‫ْ ُ َ‬ ‫ﻘﺎل ﺗﻌﺎﻠﻰ‪ :‬وﻠﻗﺪ ﺧﻟﻗﻨﺎ اﻹﻧﺳﺎن ِﻤﻦ ﺴﻼﻠ ٍﺔ ِﻤﻦ ِﻃ‬ ‫َ‬ ‫ْ‬ ‫َ‬ ‫َ‬ ‫ْ‬ ‫َ‬ ‫ََ‬ ‫َﻤﻛﻴﻦ)( ُﺛﻢ َﺧ َﻟ ْﻗ َﻨﺎ اﻠﻨ ْﻄ َﻔ َﺔ َﻋ َﻟ َﻗ ًﺔ َﻓ َﺨ َﻟ ْﻗ َﻨﺎ ْاﻠ َﻌ َﻟ َﻗ َﺔ ُﻤ ْﻀ َﻐ ًﺔ َﻓ َﺨ َﻟ ْﻗ َﻨﺎ ْاﻠ ُﻣ ْﻀ َﻐ َﺔ ﻋ َﻈﺎﻤﺎً‬ ‫ِ‬ ‫ٍ‬ ‫ِ‬ ‫َ‬ ‫َ‬ ‫َ َ َ َْ ْ َ َ َ ْ ً ُ ْ َ َ ُ َْ ً ٓ ََ َََ َ َ ُ ْ َ ُ ْ‬ ‫ﻓﻛﺳﻮﻧﺎ اﻠ ِﻌﻈﺎم ﻠﺤﻣﺎ ﺛﻢ اﻧﺷﺎﻧﺎﻩ ﺧﻟﻗﺎ اﺧﺮ ﻓﺘﺒﺎرك اﻠﻟﻪ اﺣﺳﻦ اﻠﺨﺎ ِﻠ ِﻗﻴﻦ ‪‬‬ ‫ٔ‬ ‫ٓ‬ ‫ﻫﺬﻩ اﻻﻳﺔ ﺗﺷﺮح اﻃﻮار ﺧﻟﻖ اﻹﻧﺳﺎن ﺑﺪﻘﺔ ﻤﺘﻨﺎﻫﻴﺔ ووﺻﻒ دﻘﻴﻖ‪ ،‬ﻓﻲ وﻘﺖ ﻠﻢ‬ ‫ٔ‬ ‫ﻳﻛﻦ اﻠﻌﻟﻢ اﻠﺒﺷﺮي ﻳﻌﺮف ﺗﻟﻚ اﻻﻃﻮار‪ ،‬وﻠﻢ ﻳﻛﻦ ﻋﻨﺪ اﻠﺒﺷﺮ وﺴﺎﺋﻞ ﻘﺎدرة ﻋﻟﻰ‬ ‫ٔ‬ ‫ُ‬ ‫ٔ‬ ‫ٔ‬ ‫ﻤﻌﺮﻓﺘﻬﺎ‪ ،‬وﻠﻢ ﻳﺒﺪا اﻠﻌﻟﻢ ﻓﻲ ﻤﻌﺮﻓﺔ ان اﻹﻧﺳﺎن ﻳﺨﻟﻖ ﻓﻲ اﻃﻮار إﻻ ﻓﻲ ﻤﻨﺘﺼﻒ‬ ‫اﻠﻗﺮن اﻠﺘﺎﺴﻊ ﻋﺷﺮ‪ ،‬ﺛﻢ ﻠﻣﺎ ﻃﻮرت وﺴﺎﺋﻞ اﻠﺘﺼﻮﻳﺮ واﻠﻛﺷﻒ اﺴﺘﻄﺎع اﻠﻌﻟﻣﺎء‬ ‫ّ‬ ‫ُ‬ ‫ٓ‬ ‫ٔ‬ ‫ٔ‬ ‫واﻻﻃﺒﺎء ﻤﻌﺮﻓﺔ ﻫﺬﻩ اﻻﻃﻮار ﺑﺪﻘﺔ وﺗﺼﻮﻳﺮﻫﺎ ﻓﻲ ﻤﺮاﺣﻟﻬﺎ اﻠﻣﺨﺘﻟﻔﺔ‪ ،‬ﻠﻛﻦ اﻠﻗﺮان‬ ‫ٔ‬ ‫ﺴﺒﻖ إﻠﻰ ذﻠﻚ ﻘﺒﻞ ا‬ ‫‪Dr. Yousif Osman Yousif‬‬ Dr. Yousif Osman Yousif  Definition: A branch of biology dealing with development of living organisms  Significance of Embryology in medicine The knowledge of the basic principles of development Will: 1. Assist in understanding relationships in gross anatomy, histology, and pathology. pathology 2. Serve the clinician in diagnosing certain conditions and in counseling parents who have an offspring with congenital malformations. malformations Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif EMBRYOLOGICAL TERMINOLOGY Dr. Yousif Osman Yousif  Oocyte (L. ovum, egg): egg) female germ or sex cells are produced in the ovaries Sperm: Derived from the Greek word sperma meaning seed. It refers to the male germ cell produced in the testes (testicles). Dr. Yousif Osman Yousif Zygote: Cell that results from the union of oocyte and sperm during fertilization Embryo: The developing human in its early stages of development (3-8 week) Dr. Yousif Osman Yousif Conceptus: Embryo and its dnexa i.e. all structures that evelop from zygote Dr. Yousif Osman Yousif  Fetus (unborn offspring) : The developing human after the embryonic period (9th week - birth) Dr. Yousif Osman Yousif  HUMAN DEVELOPMENT  Is divided into: 1. Prenatal period 2. Postnatal period Dr. Yousif Osman Yousif  PRENATAL PERIOD 1. Pre-embryonic embryonic or Germinal period: first 2 weeks 2. Embryonic Period 3. Fetal Period Dr. Yousif Osman Yousif  Embryonic Period/ Period of Organogenesis: 3-8 weeks Process of progressing from a single cell till the formation of organ primordia Dr. Yousif Osman Yousif Fetal Period: 9 th week – birth Differentiation continues while the fetus grows and gains weight Dr. Yousif Osman Yousif  POSTNATAL PERIOD Neonate: birth -1 month Infancy: 1st year after birth Childhood : A period from 13th month till puberty Puberty (period of development of sex characteristics) In females-12-15 years In males: 13-16 years Adolescence (period of rapid physical and sexual maturity): 11-19 years Adult hood (Attainment of full growth and maturity) is reached between the ages of 18 and 21 years. There after developmental changes occur very slowly. Dr. Yousif Osman Yousif  Development does not stop at birth. Important changes in addition to growth occurs after birth such as development of teeth and development of female breasts. The brain triples in weight b/w birth and 16 years; most developmental changes are completed by the age of 25. Dr. Yousif Osman Yousif  Gametogenesis It is the process by which mature sperm and ovum are formed. It is either spermatogenesis (sperm formation) or oogenesis (ovum formation). Dr. Yousif Osman Yousif  Male Reproductive System  Is formed of: A. Internal genital organs B. External genital organs Epididymis Penis Vas deferens Scrotum & Seminal vesicle Testis Ejaculatory duct Urethra Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif  Testis Small, oval organ, housed in the scrotum Coverings: 1. Serous membrane called tunica vaginalis: Parietal layer Visceral layer. 2. Tough fibrous capsule called Tunica albuginea: Forms internal septa 250 lobules per testis –Each lobule has up to 4 seminiferous tubules Functions: form sperms and secrete androgens. Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Testes Series of tubes: 1. Seminiferous tubules 2. Straight ducts 3. Rete testis 4. Efferent ductules 5. Epididymis 6. Ductus deferens Dr. Yousif Osman Yousif  The testes Descent of the testes –Movement of testes through inguinal canal into scrotum –Occurs during fetal development Dr. Yousif Osman Yousif The Descent of the Testes Dr. Yousif Osman Yousif Epididymis Location: behind the testis. Formed of: – Head, body and tail. Coiled tube (6 m) long Function: store & nourishment the sperms & allow them to mature The tube emerges from the tail of the epididymis as the vas deferens Dr. Yousif Osman Yousif Vas Deferens Also called Ductus Deferens Is a thick-walled tube, 45 cm long. Function: conveys mature sperm from the epididymis to the ejaculatory duct and the urethra Dr. Yousif Osman Yousif  Urethra Transports semen from the ejaculatory duct to the outside of the body. Subdivided into: 1. Prostatic urethra that extends through the prostate gland 2. Membranous urethra that travels through the urogenital diaphragm 3. Penile urethra that ends through the penis Sperm leave the body through the urethra. Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif  The Penis  The penis is male copulatory organ.  It is common outlet are urine and semen.  It is composed of:- Root Body Glans penis Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Gametogenesis (MEIOSIS ) Dr. Yousif Osman Yousif  Spermatogenesis Process of sperm formation in the seminefrous tubultes. Regulated by LH & FSH PGCs stay dormant from 4th week till puberty. Then it enter meiosis and produce sperm from puberty until death. Dr. Yousif Osman Yousif Spertomagenesis It has two parts:. Spermatocytogenisis: the development of spermatids from spermatogonia.. Spermiogenisis:: the process that converts spermatids into mature sperm (spermatozoa). Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif  Sperm production: Spermatogenesis Sperm production takes place in seminiferous tubules Seminiferous tubules contain sustencular cells and stem cells called spermatogonia Stem cells involved in spermatogenesis Sustencular cells sustain and promote development of sperm Interstitial cells between seminiferous tubules secrete sex hormones (testosterone) Dr. Yousif Osman Yousif  Sperm production: Spermatogenesis Spermatogenesis involves three processes –1) Mitosis In this process spermatocytes are produced from spermatogonium –2) Meiosis In this process spermatocytes go through meiosis I and meiosis II and produce 4 spermatids –3) Spermiogenesis In this process spermatids differentiate into spermatozoa Dr. Yousif Osman Yousif Sperm production: Spermatogenesis Dr. Yousif Osman Yousif Figure 2 perm production: Spermatogenesis Dr. Yousif Osman Yousif perm production: Spermatogenesis Dr. Yousif Osman Yousif perm production: Spermatogenesis Dr. Yousif Osman Yousif perm production: Spermatogenesis Dr. Yousif Osman Yousif perm production: Spermatogenesis Dr. Yousif Osman Yousif  Anatomy of spermatozoon Each spermatozoon is divided into 3 part: –1) Head that contains: Nucleus and densely packed chromosomes 2)) Middle piece that contains –2) Mitochondria that produce the ATP needed to move the tail –3) Tail The only cell with flagellum in the human body It enables the spermatozoa to swim Dr. Yousif Osman Yousif Spermiogenesis and Spermatozoon Structure Dr. Yousif Osman Yousif  Spermiogenisis 1. Formation of the acrosome. 2. Condensation of the nucleus. 3. Formation of the neck, middle piece, and tail. 4. Shedding of most of the cytoplasm. Dr. Yousif Osman Yousif  In humans, time required for a spermatogonium to develop into mature spermatozoon is 74 days. All sperms have 22 autosome and either an x or y chromosome. Affected by hormones, temp, radiation and drugs. Production: 300 million sperm cells/day. 50% of sperms becomes motile after 2 hrs. Dr. Yousif Osman Yousif FEMALE GENITAL SYSTEM Dr. Yousif Osman Yousif  ovaries Fallopian tubes Internal genital organs Uterus Vagina Dr. Yousif Osman Yousif  Ovary  Female primary sex organ.  Paired, almond-shaped  Size: 3*2*1 cm  Site: Usually lies in on the side wall of the pelvis in a depression called ovarian fossa. fossa  Formed of: Cortex- contains developing oogonia. Medulla- contains connective tissue & blood vessels. Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Posterior View Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif  Functions  Production of ova.  Syntheses and secretion of female sex hormones. Dr. Yousif Osman Yousif Uterine tubes (Fallopian tubes)  Muscular tube (10 cm).  Has two ends: Medially into cornu Laterally into peritoneal cavity  Formed of four parts:- Infundibulum-Ampulla Ampulla-Isthmus-Intramural. Dr. Yousif Osman Yousif Posterior View Dr. Yousif Osman Yousif  Functions  Receives the ovum from the ovary.  Site for fertilization.  Provides nourishment.  Transport ova to the uterus.  Conduit for spermatozoa to reach the ovum.  Syntheses and secretion of female sex hormones. Dr. Yousif Osman Yousif  Uterus  Thick-walled muscular organ (8*5*3 cm).  Hollow, pear-shaped, shaped, formed of:- of: 1. Fundus:: the upper part. 2. Body:: the middle large part. 3. Cervix: the lower part which projects into the vagina. Dr. Yousif Osman Yousif Fundus Body cervix Vagina Dr. Yousif Osman Yousif   Cervix: Pierces th anterior wall of th vagina & is divide into: 1. Supravaginal par 2. Vaginal part. Cervix Anterior wall of vagina Dr. Yousif Osman Yousif  Normal Position of the Uterus  Anteversion: long axis of the uterus is bent forward on the long axis of the vagina  Anteflexion: long axis of the body of the uterus is bent forward at the level of the internal os with the long axis of the cervix. cervix Dr. Yousif Osman Yousif  A B Anteverted position the uterus. Anteverted and nteflexed position f the uterus Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif Frontal Section Endometrium Myometrium Perimetrium Dr. Yousif Osman Yousif  Functions  Serve as a site for reception, retention, & nutrition of the fertilized ovum. Dr. Yousif Osman Yousif  Vagina Muscular canal 10 cm long It is upper part lies in the pelvis It is lower part lies in the perineum The anterior wall is pierced by the cervix. Dr. Yousif Osman Yousif  Midsagittal Section Dr. Yousif Osman Yousif  Functions  Female genital canal.  Excretory duct for the menstrual flow.  Forms part of the birth canal. Dr. Yousif Osman Yousif  Oogenesis Oogenesis is the process of ovum production It occurs monthly in ovarian follicles Part of ovarian cycle Follicular phase (preovulatory) Luteal phase (postovulatory) Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif  Oogenesis Primordial germ cells oogonia mature oocyte. Occurs in the ovaries Start before birth till menopause.  Prenatal maturation: 1. Oogonia proliferate by mitosis. 2. Some of them arrest their cell division in the prophase of meiosis 1 & form primary oocytes. (Diplotine stage) By the 5th month 7 million. By the 7th month degeneration occurs (2 ( million). Primordial follicle:: primary oocytes surrounded by flat epith cell Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif MITOTIC DIVISION Dr. Yousif Osman Yousif  Gametogenesis (MEIOSIS ) ry oocyte arrest in rophase of meiosis 1. End at ovulation & form ry Oocyte + Polar b. ell enter meiosis 2 ut arrest in meta- hase. End if fertilization ccurs Dr. Yousif Osman Yousif MEIOTIC DIVISION Dr. Yousif Osman Yousif rimordial follicle: primary oocytes surrounded by flat epith cell Dr. Yousif Osman Yousif Postnatal Postnatal maturation:  Primary oocytes remain arrested in prophase & do not finish their first meiotic division before puberty is reached. 1. At birth 600,000-800,000 000 primary oocytes. 2. At puberty 40,000 primary oocytes. 3. Less than 500 will be ovulated. Age is a risk factor of chromosomal abnormalities. Dr. Yousif Osman Yousif At puberty, a pool of growing follicles is established & continuously maintained from the supply of primordial follicles. Each month, 15 to 20 follicles begin to mature, accumulate fluid in space called the antrum. Prior to ovulation, it become swollen & called Graffian follicles. follicles Only 1 reach full maturity. Dr. Yousif Osman Yousif Development of the follicle Dr. Yousif Osman Yousif Development of the follicle Ovarian C.T Dr. Yousif Osman Yousif Dr. Yousif Osman Yousif  First meiotic division complete before ovulation secondary oocyte + first polar body Second meiotic division complete after fertilization mature oocyte + second polar body Dr. Yousif Osman Yousif Completion of second meiotic division. Second polar body receive little cytoplasm. Definitive oocyte. Chromosomes arranged in pronucleus and replicate. Fusion zygote (diploid) half paternal, half maternal. Dr. Yousif Osman Yousif  chromosome Traits of a new individual are determined by specific genes on chromosomes inherited from the father and the mother. 46 chromosomes arranged in 23 identical pairs. Dr. Yousif Osman Yousif First 22 pairs are called autosomes Last pair are the sex chromosomes XX female or XY male Diploid: Having the full chromosome number (46 in humans). Haploid:: Having half the full chromosome number (23 in human gametes). Dr. Yousif Osman Yousif References 5th EDITION Dr. Yousif Osman Yousif BOOK 1 BOOK 2 THE END Dr. Yousif Osman Yousif