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Endocrine system > Ejaculation and Erection > Flashcards

Ejaculation and Erection Flashcards

1
Q

Describe the structure of the seminiferous tubules (ST) and their role in sperm production.

A

The seminiferous tubules make up the parenchyma of the testes and are the site of spermatogenesis (sperm production). They are primarily composed of Sertoli cells, also known as sustentacular cells or nurse cells. Tight junctions (Claudins and Occludins) and adherent junctions (Cadherins) between Sertoli cells form a barrier known as the blood-testes barrier, preventing sperm and its antigens from leaking into the bloodstream. The ST is divided into two compartments: the basal compartment toward the basal lamina and the adlumenal compartment toward the lumen.

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2
Q

Explain the process of spermatogenesis, including the different cell types involved.

A

Spermatogenesis begins during puberty. In the basal compartment of the seminiferous tubules, there are diploid stem cells called spermatogonia. Spermatogonia undergo mitosis, producing two identical cells: one remains as a spermatogonium, and the other (B cell) moves to the adlumenal compartment. Chemicals secreted by spermatogonia cause Sertoli cells to open tight junctions. In the adlumenal compartment, the B cell is now considered a primary spermatocyte, which undergoes meiosis I to form two secondary spermatocytes. Each secondary spermatocyte divides into two spermatids through meiosis II. Spermatids are haploid cells that undergo further maturation to become spermatozoa.

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3
Q

Explain the process of crossing over during spermatogenesis.

A

During meiosis, specifically in meiosis I, homologous chromosomes (maternal and paternal) come together and fuse to form a tetrad. Crossing over, also known as recombination or synapsis, occurs within the tetrad. It involves the exchange of genetic material between homologous chromosomes, leading to a mixing of maternal and paternal genetic material. This process increases genetic diversity. The fused dyads are separated during meiosis, resulting in each daughter cell receiving a combination of chromosomes from both parents.

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4
Q

Describe the final process of transformation from spermatid to spermatozoa.

A

The final process of transformation from spermatid to spermatozoa is called spermiogenesis. Spermatozoa are more well-formed sperm cells with three well-defined parts: head, midpiece, and tail. The head contains the nucleus, which holds DNA, and the acrosome, containing hydrolytic enzymes for penetrating the egg. The midpiece has mitochondria, producing ATP for energy. The tail, a flagellum with a 9+1 arrangement of microtubules, propels the sperm. Sertoli cells secrete nutrients and metabolic products for sperm maturation during the journey to the epididymis.

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5
Q

What are the three main parts of mature sperm cells, and what are their functions?

A

Mature sperm cells have three main parts: head, midpiece, and tail. The head contains the nucleus (DNA) and the acrosome, which contains hydrolytic enzymes for penetrating the egg. The midpiece contains mitochondria, producing ATP for energy. The tail is a flagellum with a 9+1 arrangement of microtubules, enabling sperm motility.

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6
Q

Explain the role of testosterone and ABP in spermatogenesis.

A

Testosterone, produced by Leydig cells in response to luteinizing hormone (LH), stimulates spermatogenesis in the seminiferous ducts and affects other tissues. Testosterone is lipophilic. Follicle-stimulating hormone (FSH) activates Sertoli cells, which produce Androgen-Binding Protein (ABP). ABP makes testosterone less lipophilic, more water-soluble, and concentrated in the lumen of the seminiferous tubules. Both testosterone and ABP are crucial for spermatogenesis.

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7
Q

Describe the feedback mechanisms involved in the regulation of testosterone and sperm levels.

A

High testosterone levels exert negative feedback on the hypothalamus and anterior pituitary, leading to a decrease in the production of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and testosterone. High sperm levels trigger Sertoli cells to release inhibin into the bloodstream, which exerts negative feedback on the hypothalamus and anterior pituitary. This feedback reduces the production of GnRH, follicle-stimulating hormone (FSH), ABP, and testosterone, ultimately decreasing spermatogenesis.

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8
Q
  1. What are the components of the penis?
A
  • Bulb<br></br> - Shaft<br></br> - Glans penis (tip)
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9
Q
  1. What is the main erectile tissue in the penis?
A
  • Corpora cavernosum (CC)<br></br> - Spongy connective tissue<br></br> - Riddled with blood vessels
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10
Q
  1. What is the role of the corpora spongiosum?
A
  • Lines the urethra<br></br> - Keeps the urethra open during ejaculation
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11
Q
  1. What can be a stimulus for an erection?
A
  • Sight of erotic stimuli<br></br> - Thought of erotic stimuli<br></br> - Tactile stimuli (touching)<br></br> - Smell
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12
Q
  1. Which areas of the brain are activated during erection?
A
  • Specific areas related to erotic stimuli<br></br> - S2-S4 area of the sacral region
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13
Q
  1. What is the role of the pelvic nerve in erection?
A
  • Innervates blood vessels within corpora cavernosum<br></br> - Innervates a few vessels in corpora spongiosum
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14
Q
  1. What chemical do parasympathetic neurons secrete?
A
  • Acetylcholine
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15
Q
  1. What is the role of acetylcholine in the erection process?
A
  • Triggers NOS (nitric oxide synthase) pathway<br></br> - Initiates the conversion of arginine to citrulline and nitric oxide (NO)
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16
Q
  1. What is the function of nitric oxide (NO) in erection?
A
  • NO flows into smooth muscle cells, activates Guanylyl cyclase<br></br> - Leads to the production of cyclic GMP (cGMP)
17
Q
  1. How does cGMP contribute to erection?
A
  • Activates enzymes, opens K+ channels<br></br> - Smooth muscle cells hyperpolarize<br></br> - Vasodilation occurs, vessels and erectile tissue expand
18
Q
  1. What is the role of phosphodiesterase type 5 (PDE5) in erection?
A
  • Degrades cGMP
19
Q
  1. How does Viagra (Sildenafil) affect erection?
A
  • Inhibits PDE5<br></br> - Increases cGMP levels<br></br> - Maintains smooth muscle relaxation and vasodilation<br></br> - Prolongs erection
20
Q
  1. Which division of the nervous system controls erection?
A
  • Parasympathetic system
21
Q
  1. What division of the nervous system controls ejaculation?
A
  • Sympathetic system
22
Q
  1. What inhibits the parasympathetic nervous system (PSNS) during ejaculation?
A
  • Descending fibers from the cerebral cortex
23
Q
  1. What stimulates the sympathetic nervous system (SNS) during ejaculation?
A
  • Descending fibers from the cerebral cortex
24
Q
  1. Where do the descending fibers synapse in the spinal cord to stimulate ejaculation?
A
  • Lateral grey horn of the spinal cord at levels T12-T2
25
Q
  1. What does the postganglionic motor neurons of the sympathetic nervous system (SNS) release during ejaculation?
A
  • Norepinephrine (NE)
26
Q
  1. Where does NE stimulate adrenergic receptors during ejaculation?
A
  • On the smooth muscle cells of the vas deferens
27
Q
  1. What is the role of the vas deferens during ejaculation?
A
  • Squeeze sperm onwards towards the ampulla
28
Q
  1. What is the ampulla, and where is it located?
A
  • A dilated region at the end of the vas deferens
29
Q
  1. What is the role of the seminal vesicle during ejaculation?
A
  • Contracts and expels seminal fluid into the common ejaculatory duct (CED)
30
Q
  1. What forms the common ejaculatory duct (CED)?
A
  • Fused vas deferens and a duct from the seminal vesicle
31
Q
  1. What is the function of the prostatic urethra during ejaculation?
A
  • Semen is pushed into the prostatic urethra
32
Q
  1. What prevents the reflux of semen into the bladder during ejaculation?
A
  • Contraction of the internal urethral sphincter, activated by adrenergic receptors
33
Q
  1. What innervates the skeletal muscles involved in ejaculation?
A
  • Pudendal (somatic) nerve
34
Q
  1. What neurotransmitter is secreted by the pudendal nerve during ejaculation?
A
  • Acetylcholine
35
Q
  1. What effect does acetylcholine have on the skeletal muscles during ejaculation?
A
  • Causes an influx of Na+
36
Q
  1. How fast is the semen propelled through the urethra during ejaculation?
A
  • 11 miles per hour
37
Q
  1. What is the peak point of the orgasm during ejaculation called?
A
  • Climactic point
38
Q
  1. What happens to the smooth muscle cells and erectile tissue after ejaculation?
A
  • Smooth muscle cells return to normal size, erectile tissue decreases in size
39
Q
  1. What triggers the return to flaccidity after ejaculation? UniNoti
A
  • Activation of the sympathetic nervous system (SNS) after ejaculation

Endocrine system (12 decks)

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