Question

Can you paraphrase the following rationale for me:

Male Reproductive System

1. Which of the following accurately describes spermiogenesis?

a. Occurs before puberty

b. Involves stem cells, meiosis, and spermatogenesis

c. Involves cytodifferentiation of early spermatids

d. Occurs in diploid cells

e. Results in the formation of primary spermatocytes

Rationale:

Spermatogenesis, the first part of sperm production involves mainly mitosis and meiosis and is followed by spermiogenesis, the final differentiation process occurring in the haploid male germ cells. Spermatogenesis begins at puberty with proliferation of stem and progenitor cells called spermatogonia Type A spermatogonia each undergo several unique clonal divisions that leave most of the cells interconnected as a syncytium. Type B spermatogonium then undergoes a final mitotic division to produce two cells that grow in size and become primary spermatocytes. Primary spermatocytes replicate their DNA, so each chromosome consists of duplicate chromatids, and enter meiosis, during which homologous chromosomes come together in synapsis, DNA recombination occurs, and two rapid cell divisions produce haploid cells. Homologous chromosomes separate in the first meiotic division, which produces smaller cells called secondary spermatocytes. Division of each secondary spermatocyte separates the chromatids of each chromosome and produces two haploid cells called spermatids each of which contains 23 chromosomes. Spermiogenesis, the final phase of sperm production, is the temperature-sensitive process by which spermatids differentiate into spermatozoas by which spermatids differentiate into spermatozoa, which are highly specialized to deliver male DNA to the ovum.

2. A man with a pituitary gonadotrophic tumor causing hyposecretion of FSH is most likely to exhibit which condition?

a. No symptoms, since he has no ovarian follicles

b. Loss of libido (sex drive)

c. Low serum testosterone levels

d. Low sperm count

e. Prostatic hypertrophy

Rationale:

Follicle-stimulating hormone (FSH) is a glycoprotein gonadotropin secreted by the anterior pituitary in response to gonadotropin-releasing hormone (GnRH) released by the hypothalamus. FSH aree composed of alpha and beta subunits. The specific beta subunit confers the unique biologic activity. FSH and LH bind to receptors in the testis and ovary and regulate gonadal function by promoting sex steroid production and gametogenesis. FSH stimulates testicular growth and enhances the production of an androgen-binding protein by the Sertoli cells, which are a component of the testicular tubule necessary for sustaining the maturing sperm cell. This androgen-binding protein causes high local concentrations of testosterone near the sperm, an essential factor in the development of normal spermatogenesis. Sertoli cells, under the influence of androgens, also secrete inhibin, a polypeptide, which may help to locally regulate spermatogenesis. Hence, maturation of spermatozoa requires FSH to completely have adequate amount and well-functioning sperm. Since levels of follicle stimulating hormone in the bloodstream are low, this condition is called hypogonadotrophic-hypogonadism.

Sufficient follicle stimulating hormone action is needed for proper sperm production. In the case of complete absence of follicle stimulating hormone in men, lack of puberty and infertility due to lack of sperm (azoospermia) can occur. Partial follicle stimulating hormone deficiency in men can cause delayed puberty and limited sperm production (oligozoospermia), but fathering a child may still be possible. If the loss of follicle stimulating hormone occurs after puberty, there will be a similar loss of fertility

3. Interstitial cells of Leydig have an important function in male gamete production. Because of this function, which of the following organelles is abundant within these cells?

a. Lysosomes

b. Smooth endoplasmic reticulum

c. Peroxisomes

d. Polyribosomes

e. Golgi complexes

Rationale:

Smooth endoplasmic reticulum synthesizes lipids, phospholipids, and steroids which are common secreted products such as those in the testes, ovaries, and sebaceous glands. Leydig cells have an eosinophilic cytoplasm rich in small lipid droplets because of an which mean an impressive network of smooth endoplasmic reticulum must be required to produce the steroid hormone testosterone that promotes development of the secondary male sex characteristics.

4. While studying a germ cell line developed from a patient’s testicular biopsy, the researcher notes that colchicine-treated cells blocked in metaphase have 46 chromosomes. From which of the following regions of the male genital tract would you expect these cells to have originated?

a. Within the rete testis

b. At the basal lamina of the seminiferous tubule

c. In the middle region of the germinal epithelium

d. Within the adluminal compartment of the seminiferous tubule

e. Within the straight tubules

Rationale:

Sertoli cells adhere to the basal lamina and their apical ends extend to the lumen of seminiferous tubules. Important in Sertoli cell function are elaborate tight occluding junctions between their basolateral membranes, which form a blood-testis barrier within the seminiferous epithelium. The tightest blood-tissue barrier in mammals, this physical barrier is one part of a system preventing autoimmune attacks against the unique spermatogenic cells, which first appear after the immune system is mature and central self-tolerance is well established.

5. Which of the following organs is normally characterized by the accumulation of corpora amylacea with increasing age?

a. Prostate

b. Seminal vesicles

c. Bulbourethral (Cowper) glands

d. Epididymis

e. Ductus (vas) deferens

Rationale:

The prostate gland is a dense organ surrounding the urethra below the bladder. The prostate consists of a collection of 30-50 tubuloacinar glands embedded in a dense fibromuscular stroma in which smooth muscle contracts at ejaculation. The tubuloacinar glands of the prostate are lined by simple or pseudostratified columnar epithelium and produce a fluid that contains a complex mixture of exosomes, various glycoproteins, enzymes, and small molecules such as prostaglandins and is stored until ejaculation.These concretions, called corpora amylacea are small spherical concretions, up to 2 mm in diameter and often partially calcified, normally present in the lumens of many prostatic tubuloacinar glands. containing primarily deposited glycoproteins and keratan sulfate may become more numerous with age but seem to have no physiologic or clinical significance

6. Within the male reproductive tract, stereocilia project from cells lining which of the following regions?                          

a.Rete testis

b. Seminiferous tubules

c. Ampulla of the ductus deferens

d. Epididymis

e. Penile urethra

Rationale:

The epididymal duct is lined with pseudostratified columnar epithelium consisting of columnar principal cells, with characteristic long stereocilia and small round stem cells. The principal cells remove most of the water and residual bodies entering the epididymis with the sperm and secrete various products, greatly changing the fluid in which sperm are suspended. In addition to the secretion of many proteins and glycoproteins by exocytosis, these epithelial cells release abundant 25-300-nm-diameter exosomes and other vesicles from multivesicular bodies and by apocrine secretion.

7. As sperm pass through the male genital ducts, proteins and low molecular-weight products are added from several sources producing semen. Which of the following provides a nutritive, fructose-rich secretion?

a. Interstitial cells of Leydig

b. Bulbourethral (Cowper) glands

c. Prostate gland

d. Epididymis

e. Seminal vesicles

Rationale:

The seminal vesicles are exocrine glands in which production of their viscid, yellowish secretion depends on testosterone. Fluid from seminal vesicles typically makes up about 70% of the ejaculate and its components include the following: Fructose (a major energy source for sperm), Prostaglandins (stimulate activity in the female reproductive tract), Fibrinogen (semen to coagulate after

Ejaculation)

8. A 20-year-old man contracts cholera during a long tour of military duty in a remote, completely undeveloped region. After a 5-day period of severe diarrhea and treatment, he gradually recovers and slowly returns to work. He is married 3 years later but after a few years of trying to conceive a child, semen analysis reveals that his sperm are few in number and malformed, and blood tests show a high titer of antibodies against sperm antigens. The causative agent of cholera, Vibrio cholera, secretes a toxin that interferes with tight (occluding) junctions. What cells in the gonad are the likely target of this toxin in the male reproductive system?

a. Spermatogonia

b. Sertoli cells

c. Myoid cells

d. Interstitial cells of Leydig

e. Differentiating spermatozoa

Rationale:

The Sertoli cells, are tall “columnar” epithelial cells, which nourish the spermatogenic

cells and divide the seminiferous tubules into two (basal and adluminal) compartments. Tight junctions between Sertoli cells establish two compartments within seminiferous tubules: a basal compartment with spermatogonia and an adluminal compartment with spermatocytes and spermatids. Important in Sertoli cell function are elaborate tight occluding junctions between their basolateral membranes,

which form a blood-testis barrier within the seminiferous epithelium. The tightest blood-tissue barrier in

mammals, this physical barrier is one part of a system preventing autoimmune attacks against the unique spermatogenic cells, which first appear after the immune system is mature and central self-tolerance is well established.

9. A 29-year-old man presents with testicular pain and a burning sensation during urination. Tests reveal the presence of Neisseria gonorrhea and penicillin is prescribed. Gonorrhea often produces acute or chronic inflammation of the testes and frequently involves the channels that connect the testis to the epididymis. What is the name of these channels?

a. The mediastinum testis

b. The rete testis

c. Efferent ductules

d. The straight tubules (tubuli recti)

e. The seminiferous tubules

Rationale:

Efferent ductile are a thin layer of circularly oriented smooth muscle cells in the walls of efferent ductules aids the movement of sperm into the duct of the epididymis. The fragility of the tissue due to its morphological structure of being delicately thin causes chronic inflammation as induced by gonorrhea

10. A 39-year-old man undergoing an extensive series of tests for infertility is found to have a genetic mutation preventing formation of a functional synaptonemal complex during meiosis, causing almost complete failure of sperm formation. Which cells would be directly affected by this mutation?

a. Primary spermatocytes

b. Spermatogonia

c. Secondary spermatocytes

  d. Spermatids

  e. Cells undergoing spermiogenesis

Rationale:

The primary spermatocyte has 46 (44 + XY) chromosomes, the diploid number, and a DNA content of 4N. Soon after their formation, these cells enter the first meiotic prophase. The genetic disorder prevents the process of meiosis phase and greatly affect the primary spermatocytes

Spermatogenesis begins at puberty with proliferation of stem and progenitor cells called spermatogonia Type A spermatogonia each undergo several unique clonal divisions that leave most of the cells interconnected as a syncytium. Type B spermatogonium then undergoes a final mitotic division to produce two cells that grow in size and become primary spermatocytes. Primary spermatocytes replicate their DNA, so each chromosome consists of duplicate chromatids, and enter meiosis, during which homologous chromosomes come together in synapsis, DNA recombination occurs, and two rapid cell divisions produce haploid cells. The primary spermatocyte has 46 (44 + XY) chromosomes, the diploid number, and a DNA content of 4N. Soon after their formation, these cells enter the first meiotic prophase. The genetic disorder prevents the process of meiosis phase and greatly affect the primary spermatocytes. Homologous chromosomes separate in the first meiotic division, which produces smaller cells called secondary spermatocytes. Division of each secondary spermatocyte separates the chromatids of each chromosome and produces two haploid cells called spermatids each of which contains 23 chromosomes

Answer 1

Question 1) correct answer - C) involves cytodifferentiation of early spermatids.

Rephrase - Spermatogenesis is production of sperm.Spermiogenesis is the cytodifferentiation of early spermatids in haploid cells. Spermatogonia are progenitor cells in which Type A spermatogonia forms syncytium.

Type B spermatogonia undergoes mitosis and forms two primary spermatocytes. Primary spermatocytes replicate via meiosis and forms haploid cells. Homologous chromosomes seperate in meiosis 1 and forms secondary speramtocytes. Division of secondary speramtocytes produces spermatids(23 chromosome). spermatids differentiate into spermatozoas by the temperature-sensitive process spermiogenesis. These spermatozoa delivers male DNA into the ovum.