Comprehensive Study Guide: General Embryology, Cell Division, Gametogenesis, and Gamete Transport

Introduction to General Embryology & Clinical Significance

• Definition of Human Development and Embryology:

  • Human development is a continuous process initiating when a female oocyte (ovum) is fertilized by a male sperm (spermatozoon).

  • Embryology is the scientific study of the complex developmental processes that transform a single-celled zygote into a fully formed multicellular infant over approximately $9\,\text{months}$.

  • The primary mechanisms driving this morphological transformation include:

  • Cell division

  • Cell migration

  • Programmed cell death (apoptosis)

  • Cellular differentiation

  • Cellular growth

  • Cellular rearrangement

• Temporal Extent of Development:

  • Development does not terminate at birth.

  • While the most critical structural changes occur during the embryonic and fetal periods, essential developmental refinements persist throughout postnatal life, including infancy, childhood, adolescence, and early adulthood.

• Intellectual and Clinical Goals:

  • Intellectual Goal: To understand the biological origin of organisms ("All the world's a stage").

  • Clinical Goal: To elucidate the etiology and pathogenesis of congenital anomalies, thereby enabling the formulation of preventative strategies.

• Clinical Manifestations of Developmental Anomalies:

  • Structural limb defects serve as classical examples of congenital malformations:

  • Congenital absence of both forearm and hand (ICD classification Q71.2).

  • Congenital absence of finger(s) with remainder of hand intact (ICD classification Q71.30).

• Scientific Research on Teratogenesis and Birth Defects:

  • Fetal Alcohol Syndrome (FAS) and Alcohol-Related Birth Defects (ARBD):

  • Groundwork research published by Kenneth R. Warren, Ph.D., and Laurie L. Foudin, Ph.D. (Alcohol Res Health, 2001; 25(3): 153–158; PMCID: PMC6707172; PMID: 11810952) traces the progression of terminology, diagnostic challenges, prevalence determination, mechanisms of alcohol-induced fetal injury, and strategies for maternal intervention and post-natal care.

  • Substance Abuse Prevalence at Liveborn Delivery:

  • Epidemiological analysis by I-Jen Pan, PhD, and Hsiao-ye Yi, PhD (Matern Child Health J., 2013 May; 17(4): 667–676; PMCID: PMC4521396; PMID: 22688539) analyzing U.S. data from 1999–2008 emphasizes the critical requirement for early behavioral interventions and clinical treatment for pregnant women abusing substances to diminish substance-affected live births.

Embryological Terminology and Timeline

• Essential Reproductive Terminology:

  • Oocyte (Ovum / Egg): The female germ cell or sex cell synthesized in the ovaries.

  • Sperm (Spermatozoon): The male germ cell or sex cell produced in the testes (testicles).

  • Zygote: The single diploid cell produced by the fusion of an oocyte and a spermatozoon during fertilization; it marks the absolute beginning of a new human individual.

  • Embryo: The developing human during its earliest developmental stage, extending from fertilization through the end of the $8\text{th}\,\text{week}$ ($56\,\text{days}$).

  • Fetus: The developing human from day $57$ ($9\text{th}\,\text{week}$) until complete emergence from the maternal body at birth.

• Divisions of Human Development:

  • Prenatal Period (Before Birth):

  • Embryonic Period: Day $1$ to Day $56$ ($8\text{th}\,\text{week}$).

  • Fetal Period: Day $57$ to Birth.

  • Postnatal Period (After Birth): Comprises infancy, childhood, adolescence, and early adulthood.

• Methods for Calculating Developmental Age:

  • Gestational Age:

  • Calculated from the presumed first day of the last normal menstrual period (LNMP).

  • Used routinely in clinical obstetrics.

  • Measure is approximately $2\,\text{weeks}$ longer than fertilization age because fertilization occurs roughly $2\,\text{weeks}$ following the LNMP (mid-menstrual cycle).

  • Fertilization Age (Fetal Age):

  • The true age of the embryo/fetus, measured directly from the precise moment of conception/fertilization.

Chromosomal Organization, Ploidy, and Cell Types

• Chromosomal Structure and Definitions:

  • Chromosome: Nuclear structures carrying DNA responsible for transmitting precise genetic instructions during cellular division.

  • Ploidy: Indicates the number of complete sets of chromosomes present within a cell.

  • N Number: Refers to the total quantitative amount of molecular DNA within a cell.

• Chromosomal Composition in Humans:

  • Human somatic (non-germline body) cells contain $46$ single chromosomes organized into $23$ homologous pairs ($2n$ diploid state).

  • In each homologous pair, one chromosome (homologue) is of maternal origin and the other is of paternal origin.

• Subdivisions of the 23 Chromosome Pairs:

  • $22\,\text{pairs}$ of autosomes (matching non-sex chromosomes).

  • $1\,\text{pair}$ of sex chromosomes:

  • $XX$ configuration yields a genetic female.

  • $XY$ configuration yields a genetic male.

  • Gametes (germ cells) undergo reduction division to contain a haploid number ($n = 23$ chromosomes); gametic fusion at fertilization restores the diploid number ($2n = 46$).

• Classification of Body Cells by Replicative Capacity:

  • Labile Cells: Continuously divide and proliferate throughout life to substitute for cells continuously lost or degraded (e.g., ductal epithelia, hematopoietic stem cells, epidermis).

  • Stable Cells: Normally quiescent cells residing in the $G_0$ phase of the cell cycle; retain the capacity to re-enter the cell cycle and divide rapidly in response to specific stimuli or tissue injury (e.g., hepatocytes of the liver, renal tubule epithelium, endocrine glands).

  • Permanent Cells: Postmitotic cells that completely lose the capacity to replicate or divide after completing maturation (e.g., skeletal muscle cells, cardiac myocytes, neurons).

Meiotic Cell Division

• Definition and Scope:

  • Meiosis is a specialized form of cell division occurring exclusively in germ cells of sexually reproducing organisms, designed to reduce the chromosomal content from diploid ($2n$) to haploid ($n$).

• Meiosis I (Reductional Division):

  • Synapsis: Pairing up of $46$ homologous duplicated chromosomes.

  • Crossing Over: Physical exchange of large DNA segments between non-sister chromatids of homologous pairs, occurring at site connections called chiasmata.

  • Alignment: Alignment of $46$ homologous duplicated chromosomes along the equatorial metaphase plate.

  • Disjunction: Separation and migration of homologous chromosome pairs to opposite cellular poles; centromeres do NOT split.

  • Cell Division: Cytokinesis produces two secondary gametocytes, each holding $23$ duplicated chromosomes ($2N$ DNA content).

• Meiosis II (Equational Division):

  • Synapsis: Absent.

  • Crossing Over: Absent.

  • Alignment: Alignment of $23$ duplicated chromosomes along the metaphase plate.

  • Disjunction: Longitudinal splitting of centromeres, separating sister chromatids into $23$ single daughter chromosomes.

  • Cell Division: Formation of four distinct haploid gametes, each containing $23$ single chromosomes ($1N$ DNA content).

• Biological Significance of Meiosis:

  • Ensures numerical constancy of species chromosomes across generations by forming haploid gametes.

  • Facilitates random assortment of maternal and paternal chromosomes.

  • Enhances genetic diversity through chromosomal segment shuffling during crossing over.

Spermatogenesis and Male Gamete Anatomy

• Overview of Gametogenesis:

  • The developmental progression wherein precursor diploid germ cells ($2n$) undergo meiotic reduction and structural differentiation to yield mature haploid gametes ($n$).

  • In males, this process is termed spermatogenesis; in females, oogenesis.

• Detailed Process of Spermatogenesis:

  • Initiates strictly at puberty within the seminiferous tubules of the testes.

  • Spermatogonia: Dormant precursor germ cells ($46,\,XY$) resting in seminiferous tubules since the fetal stage proliferate by mitosis at puberty.

  • Primary Spermatocytes: Spermatogonia enlarge and differentiate into primary spermatocytes ($46,\,XY$), representing the largest germ cells in the seminiferous tubules.

  • First Meiotic Division: Primary spermatocytes undergo reduction division to form two haploid secondary spermatocytes ($23,\,X$ or $23,\,Y$), which are approximately half the size of primary spermatocytes.

  • Second Meiotic Division: Secondary spermatocytes undergo equational division to form four haploid spermatids ($23,\,X$ or $23,\,Y$), roughly half the size of secondary spermatocytes.

  • Spermiogenesis: Structural transformation converting non-motile, spherical spermatids into four mature, flagellated spermatozoa.

  • The complete cycle of spermatogenesis (including spermiogenesis) requires approximately $2\,\text{months}$ ($60\text{--}64\,\text{days}$).

• Supporting Structures and Male Reproductive Anatomy:

  • Sertoli Cells: Line the seminiferous tubules, providing metabolic support, protection, and regulatory signals to developing germ cells.

  • Epididymis: Elongated coiled tubule along the posterior border of the testis where immotile sperms undergo storage and acquire functional motility.

  • Ductus Deferens (Vas Deferens): Muscular tube that propels sperms from the epididymis to the ejaculatory duct and urethra via peristaltic contractions.

• Morphology of Mature Spermatozoa:

  • Head: Contains the condensed haploid nucleus ($23$ chromosomes). The anterior two-thirds is cap-topped by the acrosome, a modified lysosomal organelle loaded with enzymes (including acrosin and hyaluronidase) essential for penetrating egg investments.

  • Neck: Short constriction linking the sperm head to the tail.

  • Tail: Motility organelle structured into three distinct zones:

  • Middle Piece (Midpiece): Contains a spirally arranged mitochondrial sheath synthesizing adenosine triphosphate (ATP) for flagellar beat.

  • Principal Piece: Longest axial structural portion of the tail.

  • End Piece (Terminal Piece): Tapered terminal flagellar tip.

Oogenesis and Ovarian Follicle Development

• Phases of Oogenesis:

  • Sequence transforming precursor oogonia into mature oocytes.

  • Begins during fetal life (prenatal), arrests until puberty, resumes monthly post-puberty, and terminates at menopause.

• Prenatal Maturation Phase:

  • Primordial germ cells migrate from the yolk sac wall to the gonadal ridge/ovary during the $5\text{th}\,\text{week}$ of gestation, differentiating into oogonia ($46,\,XX$).

  • Oogonia multiply rapidly via mitosis; by the $5\text{th}\,\text{month}$ of prenatal life, total germ cell content reaches a peak of approximately $7\,\text{million}$.

  • Degeneration (atresia) commences shortly thereafter.

  • By the $7\text{th}\,\text{month}$, most oogonia have degenerated except for those near the ovarian surface.

  • Critical Note: Zero oogonia remain at birth.

  • All surviving primary oocytes enter Prophase I of Meiosis I before birth and arrest in the diplotene (dictyate) stage.

  • Each arrested primary oocyte is encircled by a single layer of flattened follicular epithelial cells, forming a primordial follicle.

  • Follicular cells secrete Oocyte Maturation Inhibitor (OMI), maintaining meiotic arrest.

• Postnatal Maturation & Folliculogenesis:

  • Total primary oocytes present at birth: $600,000\text{--}800,000$.

  • Primary oocytes remaining at puberty: \sim 40,000$.\n - Total oocytes ovulated during female reproductive lifespan: fewer than 500$($\sim 400\text{--}500).\n - *Follicular Progression Steps:*\n - **Primordial Follicle:** Primary oocyte surrounded by flat squamous follicular cells.\n - **Primary Follicle:** Follicular cells turn cuboidal then columnar (granulosa cells); an extracellular layer of glycoprotein called the **zona pellucida** forms between oocyte and granulosa cells.\n - **Secondary (Vesicular) Follicle:** Surrounding ovarian stroma condenses into the **theca folliculi**, dividing into an inner vascular/secretory layer (**theca interna**) and outer fibrous coat (**theca externa**). Fluid-filled spaces between granulosa cells coalesce into a single cavity, the **antrum**, filled with liquor folliculi. The oocyte is displaced laterally on a granulosa mound called the **cumulus oophorus**.\n - **Graafian (Mature Vesicular) Follicle:** Expands to a diameter of \ge 25\,\text{mm}.\n\n\n\n- **Completion of Meiotic Divisions:**\n - Just prior to ovulation under the influence of LH, the primary oocyte completes Meiosis I, dividing unevenly into:\n - A large **secondary oocyte** (23,\,X) containing virtually all the cytoplasm.\n - A minute, non-functional **first polar body** located in the perivitelline space between the cell membrane and zona pellucida (may occasionally undergo Meiosis II).\n - The secondary oocyte enters Meiosis II and arrests at **Metaphase II** approximately 3\,\text{hours} before ovulation.\n - Meiosis II is completed **only if fertilization occurs** by a sperm, yielding a mature fertilized egg (zygote) and a **second polar body**.\n - If unfertilized, the secondary oocyte degenerates within 24\,\text{hours} post-ovulation.\n\n# Female Reproductive Cycles and Hormonal Regulation\n\n- **Anatomical System Integration:**\n - Reproductive cycles begin at puberty and involve orchestrated signals between the hypothalamus, anterior pituitary gland, ovaries, uterine tubes, uterus, vagina, and mammary glands.\n\n- **Hypothalamic-Pituitary-Ovarian Axis:**\n - **GnRH (Gonadotropin-Releasing Hormone):** Synthesized by neurosecretory cells in the hypothalamus; travels via hypophysial portal vessels to the anterior pituitary.\n - **FSH (Follicle-Stimulating Hormone):** Stimulates growth and maturation of ovarian follicles and estrogen secretion by granulosa cells.\n - **LH (Luteinizing Hormone):** Triggers final maturation, induces ovulation (rupture of follicle and secondary oocyte release), and converts remaining follicular structures into the corpus luteum, stimulating progesterone secretion.\n\n- **Ovarian Cycle Events:**\n - Cyclic follicle growth induced early by FSH and late by LH.\n - Estrogen synthesis by growing follicles regulates female secondary sex characteristics and uterine endometrial preparation.\n - Ovulation followed by luteal conversion.\n\n# Gamete Transport, Capacitation, and Fertilization\n\n- **Oocyte Transport Mechanisms:**\n - At ovulation, the secondary oocyte, enveloped by the zona pellucida and radiating cumulus cells (**corona radiata**), is discharged from the ovarian stigma.\n - Fimbriae at the tubal infundibulum sweep over the ovarian surface.\n - Ciliary motion of mucosal epithelial cells combined with fluid currents draw the secondary oocyte into the infundibulum.\n - Peristaltic contractions of muscular walls propel the secondary oocyte into the **ampulla of the uterine tube** (the site of fertilization).\n\n\n\n- **Sperm Transport and Ejaculate Dynamics:**\n - Ejaculate Volume: Average 3.5\,\text{mL}$(range$2\text{--}6\,\text{mL}).\n - Normal Sperm Count: > 100\,\text{million sperms/mL}.\n - Sperm represents $< 10\%$ of semen volume; remaining volume consists of accessory gland fluids (seminal vesicles, prostate, bulbourethral glands).\n - Deposition: 200\text{--}600\,\text{million} spermatozoa deposited in the vaginal fornix and around the external os of the cervix during coitus.\n - Motility rate: Sperms travel at 2\text{--}3\,\text{mm/min}; movement is impeded by acidic vaginal environments and accelerated in alkaline uterine environments.\n - Key Seminal Components:\n - **Vesiculase:** Enzyme from seminal vesicles that coagulates ejaculate, producing a temporary vaginal plug to prevent semen backflow.\n - **Prostaglandins:** Stimulate uterine muscle contractions to accelerate sperm movement.\n - **Fructose:** Secreted by seminal vesicles to provide energy for flagellar beat.\n - **Cervical Mucus:** Becomes thinner and less viscid under high estrogen levels near ovulation.\n - Only \sim 300\text{--}500$spermatozoa reach the fertilization site in the ampulla. Transit time can be as fast as$5\,\text{minutes}$(up to$45\,\text{minutes}).\n\n- **Capacitation and the Acrosome Reaction:**\n - **Capacitation:** A \sim 7\text{-hour} physiological conditioning process inside the female reproductive tract required for sperms to acquire fertilizing ability. Involves removal of a glycoprotein coat and seminal plasma proteins from the sperm plasma membrane over the acrosomal region.\n - **Acrosome Reaction:**\n - Capacitated sperm binds to glycoprotein receptor **ZP3 (Zona Protein 3)** on the zona pellucida.\n - Perforations in the outer acrosomal membrane release enzymes (e.g., acrosin) that degrade the zona pellucida, allowing the sperm head to contact the oocyte plasma membrane.\n - **Cortical Block to Polyspermy:** Fusion of sperm and oocyte membranes triggers the release of lysosomal enzymes from oocyte cortical granules (**zona reaction**), altering zona pellucida properties to prevent additional sperm entry and inactivating ZP3 binding sites.\n\n\n\n# Clinical Correlates & Male Infertility\n\n- **Fertility Thresholds in Males:**\n - **Normal Count:** > 100\,\text{million sperms/mL}.\n - **Fertile Threshold:** 20\text{--}50\,\text{million sperms/mL}$(or$50\,\text{million} total per ejaculate).\n - **Sterility Threshold:** < 10\,\text{million sperms/mL} (especially when combined with immotile or morphologically abnormal sperms).\n - **Motility Requirement:** At least 50\%$of spermatozoa should demonstrate active motility$2\,\text{hours} post-ejaculation.\n\n- **Etiology of Male Infertility (Accounts for 30%–50% of Couple Infertility):**\n - Low sperm concentration (oligozoospermia/azoospermia).\n - Reduced sperm motility (asthenozoospermia).\n - Abnormal structural morphology (teratozoospermia).\n - Environmental toxins, endocrine dysfunction, cigarette smoking, excessive alcohol intake, prescription drugs, or ductal obstructions (e.g., vas deferens blockage).\n\n- **Vasectomy:**\n - Surgical excision of a segment of each ductus (vas) deferens.\n - Represents the most effective form of permanent male contraception (surgically reversible in $> 50\%$ of cases).\n - Ejaculate volume remains virtually unchanged (accessory gland fluids continue to be produced), but contains zero spermatozoa.\n\n- **Dispermy:**\n - An abnormal fertilization process occurring when two spermatozoa penetrate a single secondary oocyte simultaneously, resulting in a triploid embryo (3n = 69 chromosomes), which invariably leads to spontaneous abortion or severe fatal malformations.\n\n# Review Questions & Assessment\n\n- **Question 1:** The somatic or body cells of most organisms contain?\n - a) 23 haploid or genomes\n - b) 4$$ haploid set or genomes

  • c) Two diploid set or genomes

  • d) Two haploid set or genomes

  • Correct Answer: d) Two haploid set or genomes

• Question 2: Chromosome condense, nuclear envelope breakdown, spindle formation?

  • a) Anaphase

  • b) Metaphase

  • c) Prophase

  • d) Cytokinesis

  • Correct Answer: c) Prophase

• Question 3: Where does spindle fibers attach to during metaphase?

  • a) DNA

  • b) Chromatid

  • c) kinetochore

  • d) Cytokinesis

  • Correct Answer: c) kinetochore

• Question 4: DNA synthesis takes place during _________ phase?

  • a) G0 phase

  • b) Prophase

  • c) Anaphase

  • d) S Phase

  • Correct Answer: d) S Phase

• Question 5: One of the purpose of studying embryology is to understand congenital anomalies including their etiology?

  • a) TRUE

  • b) FALSE

  • Correct Answer: a) TRUE

• Question 6: _______ transform the fertilized oocyte (zygote), into a multicellular human being except?

  • a) Cell division

  • b) Cell Migration

  • c) Cell Rearrangement

  • d) Cell placing

  • Correct Answer: d) Cell placing

• Question 7: The Union of oocyte and sperm during fertilization is refers to as ____ ?

  • a) Oogenesis

  • b) Spermatogenesis

  • c) Zygote

  • d) Fusion

  • Correct Answer: c) Zygote

• Question 8: Embryo age is not determined from the presumed first day of the last normal menstrual period?

  • a) TRUE

  • c) FALSE

  • Correct Answer: c) FALSE (Gestational age is clinically measured from the LNMP)

• Question 9: Phosphorylation of histone leads to ______

  • a) Chromosome condensation

  • b) Cell membrane Condensation

  • c) Nuclear envelope breakdown

  • d) Spindle formation

  • Correct Answer: a) Chromosome condensation

• Question 10: Permanent cells include the following..?

  • a) Hematopoietic stem cells

  • b) Skeletal muscle cells

  • c) Labile cells

  • d) Hepatocytes

  • Correct Answer: b) Skeletal muscle cells

• Question 11: The process by which diploid or haploid cells undergo cell division and differentiation to form mature haploid gametes?

  • a) Interphase

  • b) Oogenesis

  • c) Gametogenesis

  • d) Cytokinesis

  • Correct Answer: c) Gametogenesis

• Question 12: ______ is the sequence of events by which spermatogonia are transformed into mature sperms

  • a) Spermatogene

  • b) Oogenesis

  • c) Gametogenesis

  • d) spermatogenesis

  • Correct Answer: d) spermatogenesis

• Question 13: Spermatogonia remain dormant at puberty

  • a) TRUE

  • c) FALSE

  • Correct Answer: c) FALSE (Spermatogonia remain dormant FROM fetal life UNTIL puberty, when proliferation begins)

• Question 14: Secondary spermatocyte subsequently undergoes 1st meiotic division to form two haploid secondary spermatocytes

  • a) TRUE

  • c) FALSE

  • Correct Answer: c) FALSE (Primary spermatocytes undergo the 1st meiotic division)

• Question 15: The entire process of spermatogenesis, which includes spermiogenesis, takes approximately 2 months

  • a) TRUE

  • c) FALSE

  • Correct Answer: a) TRUE

• Question 16: Gamete transport statement accuracy:

  • a) Oocytes are transported passively from the seminiferous tubules to the epididymis

  • b) Sperms are transported passively from the seminiferous tubules to the epididymis

  • c) Sperms are transported passively from the Ductus deferens to the epididymis

  • d) Sperms are transported passively from the seminiferous tubules to the epididymis

  • Correct Answer: b) Sperms are transported passively from the seminiferous tubules to the epididymis

• Question 17: _______ is the sequence of events by which oogonia are transformed into mature oocytes

  • a) Gametogenesis

  • b) Ovogenesis

  • c) Spermatogenesis

  • d) Oogenesis

  • Correct Answer: d) Oogenesis

• Question 18: Peak germ cell accumulation in prenatal ovary:

  • a) By the 5th month of prenatal development, the total number of germ cells in the ovary reaches its maximum, which is estimated at 7 million

  • b) By the 5th month of prenatal development, the total number of germ cells in the ovary reaches its maximum, which is estimated at 5 million

  • c) By the 7th month of prenatal development, the total number of germ cells in the ovary reaches its maximum, which is estimated at 5 million

  • d) By the 6th month of prenatal development, the total number of germ cells in the ovary reaches its maximum, which is estimated at 7 million

  • Correct Answer: a) By the 5th month of prenatal development, the total number of germ cells in the ovary reaches its maximum, which is estimated at 7 million

• Question 19: Oogonia presence at birth:

  • a) 2 Oogonia are present at birth

  • b) 200 Oogonia are present at birth

  • c) 200 million Oogonia are present at birth

  • d) No Oogonia are present at birth

  • Correct Answer: d) No Oogonia are present at birth

• Question 20: Events during ovulation:

  • a) During ovulation, the primary oocyte with the escaping follicular fluid are expelled from the ovarian follicle

  • b) During ovulation, the primary oocyte with the escaping follicular fluid are expelled from the zona pellucida

  • c) During ovulation, the secondary oocyte with the escaping follicular fluid are expelled from the ovarian follicle

  • d) During ovulation, the secondary oocyte with the escaping follicular fluid are expelled from the zona pellucida

  • Correct Answer: c) During ovulation, the secondary oocyte with the escaping follicular fluid are expelled from the ovarian follicle

• Question 21: Sperm production and storage sites:

  • a) Sperms are produced in the seminiferous tubules, and they are temporarily stored in the epididymis

  • b) Sperms are produced in the epididymis, and they are temporarily stored in the prostate

  • c) Sperms are produced in the epididymis, and they are temporarily stored in the testis

  • d) Sperms are produced in the seminiferous tubules, and they are temporarily stored in the prostate

  • Correct Answer: a) Sperms are produced in the seminiferous tubules, and they are temporarily stored in the epididymis

• Question 22: Requirement for sperm fertilizing capacity:

  • a) In order for the sperms to fertilize the oocytes, glycoprotein coat and seminal plasma proteins must be kept intact

  • b) In order for the sperms to fertilize the oocytes, acrosome and seminal plasma proteins must be kept intact

  • c) In order for the sperms to fertilize the oocytes, glycoprotein coat and seminal plasma proteins must be removed

  • d) In order for the sperms to fertilize the oocytes, glycoprotein coat and zona pellucida must be removed

  • Correct Answer: c) In order for the sperms to fertilize the oocytes, glycoprotein coat and seminal plasma proteins must be removed

• Question 23: Normal sperm concentration in healthy ejaculate:

  • a) There are usually 10 million sperms per milliliter of semen in the ejaculate of normal males

  • b) There are usually more than 100 million sperms per milliliter of semen in the ejaculate of normal males

  • c) There are usually more than 100 million sperms per milliliter of semen in the ejaculate of abnormal males

  • d) There are usually 10 million sperms per milliliter of semen in the ejaculate of abnormal males

  • Correct Answer: b) There are usually more than 100 million sperms per milliliter of semen in the ejaculate of normal males