Gametogenesis 2024 PDF

 Instructor information Contact: DR. Mona Abdelatty Ahmed Anatomy Department. email: [email protected] Mobile: 01063441188  Learning Outcomes By the end of the lecture, the students will be able to recognize:  Gametogenesis  Steps of spermatogenesis  Steps of oogenesis ...

 Instructor information Contact: DR. Mona Abdelatty Ahmed Anatomy Department. email: [email protected] Mobile: 01063441188  Learning Outcomes By the end of the lecture, the students will be able to recognize:  Gametogenesis  Steps of spermatogenesis  Steps of oogenesis  Case scenario  A 32-year-old male presents to the fertility clinic with his wife. They have been trying to conceive for 18 months without success. The female partner's gynecological examination and ovulation studies have come back normal, so the fertility specialist recommends a semen analysis for the male partner. Motility: 20% Total Sperm Count 5 million/ ml  What is your diagnosis  Define spermatogenesis  Enumerate steps of spermatogenesis  What is spermiogenesis MITOSIS DIFFERENCE BETWEEN MITOSIS & MEIOSIS  Gametogenesis The process by which a haploid cell (n) is formed from a diploid cell (2n) through meiosis and cell differentiation. Gametogenesis makes sex cells by meiosis Gametogenesis – gamete formation by meiosis. Spermatogenesis – Sperm formation (1N) Oogenesis – Egg formation (1N)  SPERMATOGENESIS Definition: Sequence of events by which the primitive germ cells (spermatogonia) are transformed into mature sperms or spermatozoa AIM: Formation of sperms with haploid number of chromosomes SITE: in the seminefrous tubules of testis DURATION: takes about two months OCCURRENCE: starts at puberty & continues throughout life SPERMATOGENESIS which Spermatogenesis 2N Primary spermatocyte Meiosis 1N Secondary 1N spermatocytes, 1N 1N 1N 1N 1N Spermatids, 1N morphogenesis 1N 1N 1N Sperm, 1N 1N  SPERMATOGENESIS STAGES:  PROLIFERATION: each spermatogonium divides by mitosis into 2 daughter spermatogonia (with diploid number of chromosomes: 44 + XY)  GROWTH: spermatogonium enlarges to form a primary spermatocyte (with diploid number)  MATURATION (BY MEIOSIS): 1. 1st meiotic division: a reduction division by which a primary spermatocyte divides into two secondary spermatocytes (haploid number of chromosomes: 22 + X or 22 + Y) 2. 2nd meiotic divison: a process of mitosis without a normal interphase (without DNA replication) through which a secondary spermatocyte divides into two spermatids (with haploid number of chromosomes)  SPERMIOGENESIS: a process by which a spermatid is transformed into a mature sperm (with haploid number)  SPERMATOGENESIS Spermatocytogensis Spermiogenesis Series of cell Morphological division to form transformation of spermatids spermatid int mature sperm  Spermiogenesis The process of transformation of a circular spermatid to a spermatozoon 4 phases:  Sperm morphogenesis (change of shape) Golgi complex nucleus mitochondrion  Acrosome Head with digestive enzymes nucleus Middle piece with mitochondria tail Mitochondria  Semen Semen is made up of fluid and of sperm. The Fluid component is produced by: The seminal vesicles produces a slightly alkaline fluid which makes up 50% of the semen fluid - The prostate gland contributes an acidic fluid containing which makes up 20% of the semen fluid. The rest is produced by:bulburethral and urethral glands  SEMEN ANALYSIS Semen Normal: 1.0–6.5 (mL) per ejaculation volume Sperm Normal: 20–150 million sperm per (mL) count Sperm Normal: At least 60% of the sperm show movement normal forward movement. (motility) At least 8 million sperm per milliliter (mL) show normal forward movement. Semen pH Normal: Semen pH of 7.1–8.0  Case scenario  A 32-year-old male presents to the fertility clinic with his wife. They have been trying to conceive for 18 months without success. The female partner's gynecological examination and ovulation studies have come back normal, so the fertility specialist recommends a semen analysis for the male partner. Motility: 20% Total Sperm Count 5 million/ ml  What is your diagnosis  Define spermatogenesis  Enumerate steps of spermatogenesis  What is spermiogenesis  Which of the following is a condition characterized by a low sperm count?  A) Teratozoospermia  B) Asthenozoospermia  C) Oligospermia  D) Azoospermia  Which of the following conditions is indicated by the complete absence of sperm in the ejaculate?  A) Teratozoospermia  B) Oligospermia  C) Azoospermia  D) Asthenozoospermia  Oogenesis  Definition: Sequence of events by which the oogonia differentiate into mature ovum.  SITE: It occurs in the outermost layers of the ovaries.  OCCURRENCE: starts during fetal life , becomes completed after puberty & continues till menopause  Oogenesis (steps) A-Prenatal maturation  During intrauterine life oogonia. Diploid (44+XX).  Each oogonia also undergoes mitosis to produce two diploid primary oocytes.  Each primary oocyte starts to undergo meiosis I but they are arrested at the first Meiotic Prophase  Oogenesis (steps) B-Postnatal maturation Meiotic block is removed by the onset of puberty. Secondary oocyte The primary oocyte First polar body (each contains 22+X).  Oogenesis (steps) B-Postnatal maturation Secondary oocyte enters Meiosis II At ovulation and is arrested at metaphase II.  Secondary oocyte completes the Meiosis II in the uterine If fertilization tube giving rise to the mature ovum + second polar body.  The first polar body also divides giving two polar bodies.  Oogensis 2N Primary Oocyte Meiosis Secondary 1N 1N Polar Body oocyte Polar 1N Polar Ootid 1N 1N 1N body bodies 1N Ovum Die Die Die Anatomy of the ovum  RESULT OF OOGENESIS Reduction of the number of chromosomes from the diploid number (46) in the oogonia to the haploid number (23) in the secondary oocyte and mature ovum DIFFERENCES BETWEEN SPERMATOGENESISAND OOGENESIS Spermatogenesis Oogenesis 1. Occurs in the testis. 1. Occurs in the ovary. 2. Starts after puberty. 2. Starts during fetal life. 3. Continues till old age. 3. Ends at menopause (45 years). 4. Every daughter spermatogonium 4. Every daughter oogonium gives gives rise to 4 equal spermatids. rise to one ovum and 3 polar bodies. 5. Every spermatid transforms to a 5. No stage of transformation motile sperm. occurs and  Sperm Ovum size Small (50µ) Large (114-142µ) Motility Highly motile immotile membranes No covering Covered by: A-zona pellucida Corona radiate cytoplasm little Abundant Contains yolk granules for nutrition of the embryo during the first week of development chromosomes 2 types22+X or 22+Y 1 type 22+X Gametogenesis means formation of gametes (Sperm & Ova). Spermatogenesis Means formation of sperm ; male gametes. Oogenesis Means formation of ovum ; female gametes. Sperm and ovum are highly specialized sex cells. Both types possess three main phases: 1. Period of multiplication: The primordial germ cells multiply by mitotic cell division giving rise to oogonia in case of females and spermatogonia in case of males. 2. Period of growth: During these phase both oogonia (female gamete) and spermatogonia (male gamete) grow into primary oocyte or primary spermatocyte. 1. Period of maturation: In case of female, the primary oocyte undergoes two meiotic cell division, the first gives rise to secondary oocyte and primary polar body. The secondary undergoes second meiotic division giving rise to mature ova and secondary polar body (mature ova leach oogonia). In case of male, each primary spermatocyte divides meiotically into secondary spermatocytes and intern to spermatid (4 spermatid l each primary spermatocyte). Spermatogenesis Primary spermatocyte Meiosis 1N 1N 1N 1N 1N 1N 1N 1N 1N Sperm, 1N 1N  Oogensis 2N Primary Oocyte Meiosis 1N 1N 1N 1N 1N Ootid 1N 1N Die Die Die  MCQ Oogenesis starts- 1. Before birth 2. After birth 3. At puberty 4. After puberty  MCQ Oogonia undergo mitosis to form- 1. Primary oocyte 2. Secondary oocyte 3. First polar body 4. Second polar body  Which of the following processes involves making sperm cells mobile? (1 mark)  Spermatogenesis  Spermiogenesis  Spermiation  Sperm capacitation  the correct sequence of cell stage in spermatogenesis is  (a) Spermatocytes – Spermatids – Spermatogonia – Spermatozoa  (b) Spermatogonia – Spermatids – Spermatocytes – Spermatozoa  (c) Spermatocytes – Spermatogonia – Spermatids – Spermatozoa  (d) Spermatogonia – Spermatocytes – Spermatids – Spermatozoa  When does oogenesis permanently cease in females? (1 mark)  At puberty  At the birth of a child  At menopause  At death  When does oogenesis begin in the female? (1 mark)  In utero  At birth  At puberty  At menopause  Which of the following equations is the most correct representation of spermiogenesis? (1 mark)  Primordial germ cells -> spermatogonia -> primary spermatocytes  Primary spermatocytes -> secondary spermatocytes  Secondary spermatocytes -> spermatids -> sperm cells  Spermatids -> sperm cells  6. The actual genetic section of sperm is its  (a) Acrosome  (b) Tail  (c) Middle piece  (d) Head  How many polar bodies are produced in total by oocyte division following fertilisation? (1 mark)  1  3  4  8  In spermatogenesis, the phases of maturation involve  (a) formation of spermatids from primary spermatocytes through meiosis  (b) Growth of spermatogonia into primary spermatocytes  (c) formation of spermatogonia from gonocytes through mitosis  (d) formation of oogonia from spermatocytes through meiosis