L40,41 and 42

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Questions and Answers

What is the main component of semen that constitutes only 5 to 10% of its volume?

Proteins

Fructose

Sperm (correct)

Fatty acids

What is the order of development for sperm cells starting from their initial form?

Secondary spermatocytes → Primary spermatocytes → Spermatids → Spermatogonia

Spermatogonia → Primary spermatocytes → Secondary spermatocytes → Spermatids (correct)

Primary spermatocytes → Spermatids → Spermatogonia → Secondary spermatocytes

Spermatids → Secondary spermatocytes → Primary spermatocytes → Spermatogonia

What structure within the sperm head is responsible for containing enzymes that help penetrate the female egg?

Acrosome (correct)

Nucleus

Midpiece

Tail

Which type of cells in the testes are responsible for sperm production? (review)

Spermatogonia Signup and view all the answers

What role does follicle stimulating hormone (FSH) play in spermatogenesis?

Stimulates Sertoli cells to convert spermatids to sperm Signup and view all the answers

How many sperm does an average male produce in a single ejaculation?

Around 200 to 500 million Signup and view all the answers

Which hormone is primarily responsible for the regulation and secretion of testosterone during adulthood?

Luteinizing hormone Signup and view all the answers

What hormone is primarily responsible for the masculine characteristics observed during development?

Dihydrotestosterone Signup and view all the answers

What triggers penile erection during the male sexual act?

Parasympathetic impulses from the sacral spinal cord Signup and view all the answers

What component of sperm provides the energy necessary for its motility?

Mitochondria Signup and view all the answers

What is the primary function of seminal fluid aside from sperm transport?

To provide nutrients to sperm Signup and view all the answers

Which gland secretes mucus during the lubrication stage of male sexual arousal?

Bulbourethral glands Signup and view all the answers

What happens to spermatogenesis in the absence of growth hormone?

Spermatogenesis is severely deficient or absent Signup and view all the answers

What does testosterone convert into within target cells?

Dihydrotestosterone Signup and view all the answers

When does testosterone production by the testis cease during early development?

After fetal life and for 10 weeks Signup and view all the answers

What occurs during the emission phase of the male sexual act?

Contraction of the prostate and seminal vesicles Signup and view all the answers

What is the primary role of the fluid secreted by sertoli cells and the epithelium of the epididymis?

To provide nourishment and facilitate sperm maturation Signup and view all the answers

Which of the following substances is NOT found in the secretion of the prostate gland?

Fructose Signup and view all the answers

What is the effect of mildly acidic environments on mature sperm?

Decreases their motility and capability of fertilization Signup and view all the answers

What is the average lifespan of ejaculated sperm in the female genital tract?

1 to 2 days Signup and view all the answers

How does sperm morphology impact fertility when sperm count is otherwise normal?

Half of the sperm being of abnormal shape may cause infertility Signup and view all the answers

Which of the following hormones is essential for the development and division of testicular germinal cells?

Testosterone Signup and view all the answers

What is considered a normal sperm count per milliliter of semen?

35 million to 200 million Signup and view all the answers

Which of the following statements regarding sperm storage in the vas deferens is accurate?

A small amount of sperm is stored here compared to the epididymis Signup and view all the answers

What is the primary reason for treating cryptorchidism before puberty?

To decrease the incidence of malignant tumors Signup and view all the answers

Which hormone is responsible for stimulating ovulation?

Luteinising Hormone (LH) Signup and view all the answers

How does the increase in estrogen during the menstrual cycle affect FSH production?

It inhibits the production of FSH Signup and view all the answers

What role does progesterone play after the egg is released during the menstrual cycle?

It maintains the lining of the uterus Signup and view all the answers

Which hormone is primarily responsible for the maturation of eggs in the ovary?

Follicle Stimulating Hormone (FSH) Signup and view all the answers

What role does testosterone play in the descent of the testis during fetal development?

It is secreted by the fetal testis during the last months of gestation. Signup and view all the answers

Which of the following is NOT an effect of testosterone on adult male primary and secondary sexual characteristics?

Increase in breast tissue development. Signup and view all the answers

How does testosterone affect hair growth in males?

It promotes hair growth in specific areas while potentially decreasing it on the scalp. Signup and view all the answers

What is one of the effects of testosterone on the skeletal system during puberty?

It facilitates the fusion of epiphyses with the shafts of bones. Signup and view all the answers

Which of the following describes testosterone's effect on the skin?

It increases skin thickness and sebaceous gland activity. Signup and view all the answers

What impact does testosterone have on muscle development after puberty?

It enhances muscle development by approximately 50%. Signup and view all the answers

What does testosterone do to the shape of the male pelvis?

It narrows and lengthens the pelvic outlet. Signup and view all the answers

In terms of voice alteration, what is a major effect of testosterone during puberty?

It causes hypertrophy of the laryngeal mucosa. Signup and view all the answers

What event occurs during days 1-4 of the menstrual cycle?

Menstruation Signup and view all the answers

Which hormone is primarily responsible for the repair of the uterus lining during the menstrual cycle?

Oestrogen Signup and view all the answers

What marks the transition from the proliferation phase to ovulation in the menstrual cycle?

Day 14 Signup and view all the answers

Which of the following is NOT a hormone involved in the menstrual cycle?

Testosterone Signup and view all the answers

Which phase of the menstrual cycle includes the breakdown of the uterus lining?

Menstruation Signup and view all the answers

Study Notes

Reproductive System Overview

The lecture covers the reproductive system, focusing on male and female aspects.
The learning objectives include understanding semen composition, ejaculation physiology, male sex hormones (testosterone), female reproductive cycles, and female sex hormones (estrogen and progesterone).

Sperm Production

Each testicle contains seminiferous tubules, crucial for sperm production.
Sperm develop from spermatogonia through primary and secondary spermatocytes, eventually becoming spermatids and then sperm.
Sperm maturation takes approximately two months.
Thousands of sperm are produced every second.

Semen Composition

Semen comprises sperm (5-10%) and a nutrient-rich fluid (fructose, fatty acids, proteins) essential for sperm survival.
A healthy ejaculate contains 200-500 million sperm.
A man produces roughly 525 billion sperm throughout his lifetime.

Sperm Structure

Sperm consists of a head (containing the nucleus with chromosomes and the acrosome with enzymes), a midpiece (with mitochondria for energy), and a tail (for motility).
The acrosome contains enzymes necessary for penetrating the female egg.
The midpiece contains mitochondria for energy to move the tail and thus the sperm.

Physiology of Erection and Ejaculation

Normal male sexual function requires intact libido, the ability to achieve/maintain erection, ejaculation, and detumescence (return to flaccid state).
The autonomic nervous system (ANS) plays a key role in these processes.

Sexual Response Cycle

The cycle comprises excitement, plateau, orgasmic, and resolution phases.
Excitement encompasses erection and heightened sexual awareness.
Intensification and body responses (increased HR, BP, RR, muscle tension) occur during the plateau phase.
Ejaculation and other culminatory responses occur during the orgasmic phase.
The resolution phase involves the return to the pre-arousal state.

Innervation of Erection

Erection is mediated by central (psychogenic) and peripheral (reflexogenic) innervation.
The central nervous system (CNS) stimulates or antagonizes spinal pathways for erection and ejaculation.
Peripheral input (reflexogenic) is involved in tactile stimulation to generate CNS response in achieving and maintaining erection.

Sexual Arousal

Tactile stimulation from the skin or glans penis initiates tactile stimulation, which reflexively triggers ↑ PSNS (parasympathetic) vasodilator activity.
This leads to the release of NO from endothelial cells and the relaxation of smooth muscle, leading to vasodilation.
Prostaglandins also play a role in smooth muscle relaxation, aiding erection.
SNS (sympathetic) inhibition contributes to erection.

Erection Mechanism

Erection involves three cylindrical vascular cords (corpora cavernosa and corpus spongiosum) that engorge with blood.
Blood flow into the erectile tissue increases, constricting outflow.
The penis becomes rigid, and the emissary veins draining the penis, are compressed, preventing blood from escaping and maintaining erection.

Ejaculation

Ejaculation, mediated by somatic motor impulses via the pudendal nerve and SNS impulses, involves rhythmic contractions of the bulbospongiosus and ischiocavernosus muscles.
Emission (expulsion of seminal fluid into the urethra), as well as semen mixing with mucous from the bulbourethral glands are vital steps.
Detumescence (return to flaccid state) is due to increased venous outflow, with NA (norepinephrine) and endothelin's role.

Sperm Maturation in Epididymis

Sperm requires several days in the epididymis to mature.
After 18-24 hours, they develop motility.
Inhibitory proteins in the epididymal fluid prevent final motility until ejaculation.

Sperm Storage

The testes produce up to 120 million sperm daily.
The majority is stored in the epididymis, maintaining fertility for up to a month.
Sperm is kept in an inactive state by multiple inhibitory substances in the ducts.

Maturation of Mature Sperm

Mature sperm are motile and capable of fertilization in a neutral/alkaline medium.
Their life expectancy within the female genital tract is short (1-2 days).

Seminal Vesicle and Prostate Gland Function

Seminal vesicles secrete a mucoid fluid containing fructose, citric acid, nutrients, and prostaglandins/fibrinogen.
The prostate gland secretes a fluid containing Calcium (Ca2+), citrate, phosphate, and enzymes essential for successful fertilization of the egg.

Effect of Sperm Count & Morphology on Fertility

Sperm count below 20 million/ml is associated with infertility.
Even with normal sperm count, abnormal morphology or motility can impact fertility negatively.

Hormonal Factors Stimulating Spermatogenesis

Testosterone, crucial for testicular growth and germinal cell division, is secreted by Leydig cells.
Luteinizing hormone (LH) stimulates Leydig cells to secrete testosterone.
Follicle-stimulating hormone (FSH) stimulates Sertoli cells and spermatid maturation into sperm.
Estrogen is crucial for spermatogenesis.
Growth hormone (GH) is vital for spermatogenesis and overall testis function.

Cryptorchidism

Cryptorchidism is the failure of the testes to descend into the scrotum.
Treatment is recommended before puberty due to the higher incidence of malignant tumors.

Menstrual Cycle

The menstrual cycle is the body's way of preparing for pregnancy, controlled by hormones.
The phases include menstruation, proliferation, and ovulation.
The cycle involves FSH, LH, estrogen, and progesterone, which regulate the maturation and release of an egg and preparation of the uterus for implantation.

Male Sexual Act

Male sexual act comprises erection, lubrication, emission, and ejaculation.
Erection is a parasympathetic process affecting the penis.
Lubrication involves secretion of mucus from bulbourethral glands.
Emission involves sympathetic stimulation of sperm and seminal fluid ducts and muscles, passing them into the urethra.
Ejaculation involves rhythmic contractions of the muscles to propel semen out of the body.

Testosterone Function

Testosterone is a crucial male sex hormone, responsible for the development and maintenance of male secondary sexual characteristics. These include increased body hair distribution on the face, chest, etc., baldness, voice thickening, and acne.
Testosterone is also responsible for muscle development.
It plays a crucial role in bone matrix formation and Ca2+ retention.
It's essential for the descent of testes into the scrotum during fetal development.

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Test your knowledge on human reproductive biology, focusing on the anatomy and physiology related to sperm production and function. Explore topics such as hormones influencing spermatogenesis and the components of semen. Ideal for students studying biology or health sciences.