Embryology Handout Lec 1, 2 Dr Manar PDF

# Lecture 1: General Embryology ## Handout By Dr/ Manar Ali Faried Ass. Prof. of Anatomy and Embryology Menoufia Faculty of Medicine ## Definition of Embryology Study of the prenatal stages and mechanisms of human development ## Gametogenesis Gamete = reproductive cell (الخلية الانجابية) Gen...

# Lecture 1: General Embryology ## Handout By Dr/ Manar Ali Faried Ass. Prof. of Anatomy and Embryology Menoufia Faculty of Medicine ## Definition of Embryology Study of the prenatal stages and mechanisms of human development ## Gametogenesis Gamete = reproductive cell (الخلية الانجابية) Genesis = production/formation ## Male Genital System | Category | Components | |---|---| | Primary Sex Organ (testis) | | | Secondary Sex Organs | | | External Genitalia | | | Ducts | epidydimis, vas deferens, ejaculatory duct, urethra | | Glands | prostate, seminal vesicle, Bulbourethral | ## Female Genital System | Category | Components | |---|---| | Primary Sex Organ (ovary) | | | Secondary Sex Organs | | | External Genitalia | | | Ducts | vagina, uterus, fallopian tube | | Glands | | ## Gametogenesis Definition: It is the process of gametes formation through cell division in the primary sex organs. ## Cell division: There are two distinct types of cell division: mitosis and meiosis, each one of them is preceded by the interphase. ### During the interphase, the DNA is replicated converting the single stranded chromosomes into double stranded chromosomes. ### 1. Mitosis Mitosis gives rise to 2 daughter cells; each one is genetically identical to the mother cell. It has four phases: prophase, metaphase, anaphase and telophase. ### 2. Meiosis Meiosis gives rise to four daughter cells (haploid gametes) through two divisions (each division has four phases). #### A. First meiotic division (meiosis I) Results: 2 daughter cells; each cell contains: 23 d-chromosomes (double-stranded). #### B. Second meiotic division (meiosis II) Results of meiotic division: 4 daughter cells; each cell contains 23 s- chromosomes (single-stranded). ## Mitosis vs. Meiosis Side By Side | Mitosis | Meiosis | |---|---| | Replication | Replication | | Cell Division | Cell Division | | Cell Division | Cell Division | | 2N daughter cells | | ## Male Gametogenesis [Spermatogenesis] Definition: It is the process of transformation of spermatogonia (diploid; 46 chromosomes cell) into spermatozoa (mature sperm) (haploid; 23 chromosomes) through cell division in the testis. Site: It occurs in the seminiferous tubules of the testis. Duration: is 2 months (roughly 60 days). Onset: started from puberty (13-16 Y) till old age. Stages: It is composed of four stages (proliferation, growth, maturation and changes in shape “spermiogenesis/transformation"). ## Stages of Spermatogenesis ### 1. Proliferation: (mitosis) increase in number of spermatogonia. Spermatogonia (46 chromosome) by mitosis gives rise to 2 daughter spermatogonia A & B (46 chromosome) ### 2. Growth: increase in size of daughter spermatogonia B to become primary spermatocyte. ### 3. Maturation: (meiosis): reduction of chromosomes #### 1st maturation: Meiosis I 1ry spermatocytes(46 d) gives 2 2ry spermatocytes (23 d) #### 2nd maturation: Meiosis II Each 2ry spermatocyte (23 d) gives 2 spermatids (23 s) ### 4. Transformation (Spermiogenesis): #### Definition: morphological transformation of the spermatids to mature sperms (spermatozoa) #### Process: The nucleus: condensed and forms most of head of the sperm. Golgi apparatus covers the anterior 2/3 of the nucleus to form the head cap or acrosomal cap of the sperm. Centrioles: directed towards the opposite side of the nucleus and elongate gradually to form the axial filament that forms the tail of the sperm. Mitochondria (sheath): surround the midpiece and it is concerned with energy production for movement. ## Sperm structure: Its length is about 60 microns and is composed of: 1. Head 2. Neck 3. Tail (longest part): midpiece, principle piece and terminal piece ## Structure of A Healthy Sperm | Part | Description | |---|---| | Head | | | Midpiece | | | Tail | | | Acrosome | | ## Spermatogonia gives rise to 4 sperms ### N.B: The sperm takes minutes (variable from 6-60 minutes) till reach the site of fertilization. About 600 million of sperms are present in each ejaculate. The sperm has the fertilization power for 1-2 days and can live for maximum 5 days in the female genital tract. ## Abnormal shape of sperms | Type | | |---|---| | Normal | | | Giant | | | Micro | | | Double Head | | | Double Body | | | Long Head | | | Rough Head | | | Abnormal Neck | | | Tail Defect | | ## Sperm and secretion from the seminal vesicle, prostate and bulbourethral glands form the semen (السائل المنوي) The ejaculate is about 1.5-5 ml The number of sperms may reach 600 million/ejaculate about 100 million sperm/ml ## Standard Test - Normal Values | Test | Normal Range | |---|---| | Volume | 1.5 - 5.0 mL | | Sperm Count | ≥39 million | | Sperm Concentration | ≥15 million/mL | | Total Motility | ≥40% | | Progressive Motility | ≥32% | | Morphology | ≥4% | | Leukocyte (WBC) count | < 1 million | | Vitality | ≥58% | | pH | 7.2-7.8 | # Lecture 2: General Embryology ## Handout --*By* Dr/ Manar Ali Faried Ass. Prof. of Anatomy and Embryology Menoufia Faculty of Medicine ## Oogenesis Definition: It is the process of transformation of oogonia (diploid; 46 chromosomes cell) into mature ovum (haploid; 23 chromosomes), the female gamete for fertilization. Site: Mostly in the outer cortex of the ovary and completed in the fallopian tube if fertilization occurs Onset: begins intrauterine and then reactivated at puberty (about 8-14 years old) till menopause (about 45-55 years old) ## Stages : 3 stages (proliferation, growth and maturation) * During intrauterine life (proliferation, growth & 1st meiotic till prophase I) * At puberty (Immediately before 1st ovulation, completion of the 1st meiotic division, the secondary oocyte starts the 2nd meiotic division and arrested in the metaphase II) * Immediately after fertilization (completion of the 2nd meiotic division to give the mature ovum and the second polar body) ### N.B: The ovary of the newborn female contains 1ry oocyte not oogonia. As all oogonia were transformed into lry oocyte before birth ### N.B: There are 2 million lry oocytes in the ovaries of the newborn females. There are only about 480 becomes 2ry oocytes and are expelled at ovulation during reproductive life (about 40 years), the remaining become atretic. ## Female Reproductive Cycles ### Ovarian Cycle #### Definition: cyclic changes in the ovaries from puberty till menopause in non pregnant females. #### Duration: average 28 days #### Cause: FSH and LH. #### Phases: three phases: * Preovulatory phase (Follicular phase) * Ovulation * Postovulatory phase (Luteal phase ) ## Preovulatory (Follicular) phase #### Maturation of the oocyte & development of the follicular cells surround it forming different types of follicles ### Primordial and follicle: Iry oocyte surrounded by a single layer of follicular cells which are at first flat cells (before birth), but later they become cuboidal (during puberty) (1ry follicle). ### Growing follicles: * Two membranes are added by the follicular cells zona pellucida & basement membrane * Follicular cells: increased and interrupted by follicular cavity (antrum). * Theca cells: externa and interna. | Type | Description | |---|---| | Primordial Follicle | | | Primary | | | Secondary | | | Preantral | | | Early antral | | | Antral | | | Graafian | | ## Mature Graafian follicle: * **Site:** in the cortex of the ovary. * **Shape:** rounded * **Time:** at 14th day * **Size:** 1-2 cm in diameter. ### Structure: from outside inwards: 1. Theca externa & interna layers 2. Follicular cells: Many layers and classified into: * **Corona radiate.** few layers of cells surrounding the ovum. * **Granulosa cells:** all around the follicle. * **Cumulus oophorus:** cells connecting corona with granulosa cells 3. The follicular cavity: filled with the follicular fluid. 4. Zona pellucida: becomes thicker. 5. Immature ovum: (100-200 micron) and immediately before ovulation becomes 2ry oocyte. ## Ovulation phase #### Definition: rupture of the mature Graafian follicle and liberation of the 2ry oocyte which surrounded by the zona pellucida and corona radiata. #### Fate: it enters the uterine tube where it is either fertilized or discharged from the uterus during the menstrual period. #### Time: mid-cycle (14th day in an average 28-day menstrual cycle) #### Causes: * FSH and LH hormones. * Prostaglandins: produces contraction of the theca externa cells. ## Postovulatory (Luteal) phase After ovulation, the wall of the Graafian follicle collapse then the following events occur: * The follicular cavity becomes filled with blood and forms the corpus haemorrhagicum. * After three days, the bleeding stopped, the granulosa cells enlarged and became distended with the yellow pigment * The follicle is transformed into a yellow body, known as corpus luteum which: * Secretes progesterone and little estrogen. * Lives for 9 days then degenerate if pregnancy doesn't occur. ## Fate of corpus luteum * **If fertilization occur** * The corpus luteum enlarges (by human chorionic gonadotrophin hormone) and continues to secrete progesterone till 4th month of pregnancy and called corpus luteum of pregnancy. * **If fertilization doesn't occur** * The corpus luteum begins to degenerate about 10 to 12 days after ovulation, the corpus luteum is, then, transformed into white fibrous tissue in the ovary called the corpus albicans. ## Hormonal Regulation of the Ovarian Cycle ### FSH * + Oocyte maturation * + Follicle maturation #### Estrogen Secretion ### LH * + theca cells to secrete androgen #### Progesterone Secretion * + Ovulation * + corpus luteum formation ### If pregnancy occurs, LH levels will decrease, and replaced by the action of HCG (human chorionic gonadotropin), a hormone very similar to LH. ## Uterine [Menstrual] Cycle ### Definition: Cyclic and structural changes in the endometrium of the uterus every 28 days ### Onset: from puberty till menopause. ### Cause: estrogen and progesterone. ### Phases: three main phases. * Menstrual (bleeding) phase. * Proliferative (estrogenic) phase. * Secretory (luteal, progesteronic) phase. ## Uterus * Uterine cavity * Perimetrium * Myometrium * Endometrium ## Endometrial Tissue * Myometrium * Basal Layer * Functional Layer * Endometrium ### N.B: Functional layer = Compact & spongy layer ### Epithelium * Uterine Gland * Secretion * Vein * Functional Layer * Basal Layer * Myometrium * Straight Artery * Helical Artery * Arcuate Artery and Vein ## Menstrual (Bleeding) phase ### Duration: usually lasts 4 to 5 days. ### Cause: Degeneration of the corpus luteum causes sudden drop of progesterone level leading to spasm of the arteries of the endometrium resulting in ischemia, necrosis, and degeneration of functional layer of endometrium ending into shedding of this layer and bleeding. ### Characters of menstrual phase: * It is the bleeding from vagina. * Amount: 50-60 c.c. * Contents: * Unclotted blood. * 2ry oocyte and its surrounding (zona pellucida and corona radiate) * Functional layer of endometrium (stratum compactum and stratum spongiosum) ## Proliferative (estrogenic) phase ### Duration: about 9 days (from the end of the menstrual phase till 14th day of the cycle "ovuolation") ### Corresponding to the growth of ovarian follicles. ### Cause: estrogen secreted by growing follicles. ### Characters of the proliferative phase: 1. Endometrium: it is 2-3 mm in thickness. 2. The glands: grow up and tortuous with some secretions inside them. 3. The arteries: elongated and coiled. ## Secretory (Luteal-Progesteronic) phase ### Duration: about 14 days, extends from the time of ovulation. ### Corresponding to the formation and growth of the corpus luteum ### Cause: progesterone and estrogen hormones produced by corpus luteum. ### Characters of the secretory phase: 1. The endometrium: 5-7 mm in thickness. 2. The glands: grow more & become wide, tortuous and full of glycogen & mucin secretions. 3. The spiral arteries: more coiled and reach the superficial layer. ### N.B: The endometrium in secretory phase divided into 3 layers: * Superficial layer (stratum compactum): contains neck of gland. * Middle layer (stratum spongiosum): contains body of gland. * Deep layer (stratum basalis): contains base of gland.