Anatomy and Physiology: Reproductive System

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Questions and Answers

What initiates the vascular changes necessary for an erection?

Increased sympathetic nervous system activity

Contraction of the corpus spongiosum

Inhibition of the parasympathetic nervous system

Vasodilation mediated by nitric oxide (correct)

Which phase of the sexual response cycle involves heightened sexual awareness and increased blood flow to the penis?

Plateau phase

Excitement phase (correct)

Resolution phase

Orgasmic phase

During which phase of ejaculation does the contraction of the epididymis and seminal vesicles occur?

Flaccid phase

Expulsion

Detumescence

Emission (correct)

Which type of innervation stimulates the erectile response through psychogenic stimuli?

Central innervation from the limbic system Signup and view all the answers

What is the primary mechanism that induces detumescence following ejaculation?

Increased sympathetic activity and hormone release Signup and view all the answers

The process by which sperm become motile takes place in which part of the male reproductive system?

Epididymis Signup and view all the answers

Which of the following physiological changes does NOT occur during the plateau phase?

Flaccidity of the penis Signup and view all the answers

What role does the internal vesical sphincter play during ejaculation?

Prevents semen from entering the bladder Signup and view all the answers

What is the primary period during which the uterine lining breaks down?

Menstruation phase Signup and view all the answers

During which phase does the repair of the uterus lining occur?

Proliferation phase Signup and view all the answers

What day is typically associated with ovulation in the menstrual cycle?

Day 14 Signup and view all the answers

Which hormone plays a crucial role in the maintenance of the uterine lining?

Oestrogen Signup and view all the answers

What is the total duration of a typical menstrual cycle?

24-28 days Signup and view all the answers

What is the primary role of the Acrosome in sperm?

To contain enzymes for penetrating the female egg Signup and view all the answers

Which part of the sperm is primarily responsible for its motility?

The tail Signup and view all the answers

How long does it take for sperm to mature after production?

Two months Signup and view all the answers

Which of the following contributes the largest proportion to semen composition?

Fructose Signup and view all the answers

What is the average sperm count in a single human ejaculation?

200 to 500 million Signup and view all the answers

What initiates the physiological process of an erection?

Neurological signals from the brain Signup and view all the answers

Sperm develop from which type of cells in the testes?

Spermatogonia Signup and view all the answers

During ejaculation, what is the primary function of the muscle contractions?

To propel sperm out of the urethra Signup and view all the answers

Which hormone primarily influences the development of male secondary sex characteristics during puberty?

Testosterone Signup and view all the answers

What is the main function of Mitochondria in the midpiece of sperm?

To provide energy for movement Signup and view all the answers

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

It promotes the conversion of spermatids to sperm by stimulating Sertoli cells. Signup and view all the answers

Which hormone is crucial for the metabolic functions of the testis and the early division of spermatogonia?

Growth hormone (GH) Signup and view all the answers

What initiates the process of penile erection?

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

During ejaculation, which gland contracts to expel its fluid into the urethra?

Prostate Signup and view all the answers

Which of the following best describes the physiological change that occurs during the emission phase of ejaculation?

Contraction of the vas deferens and ampulla Signup and view all the answers

How is estrogen related to testosterone in the context of spermatogenesis?

Estrogen is produced from testosterone by Sertoli cells under FSH stimulation. Signup and view all the answers

In the absence of growth hormone, what happens to spermatogenesis?

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

Which of the following hormones is primarily responsible for the characteristic masculine body?

Testosterone Signup and view all the answers

What happens to testosterone production after 80 years of age?

It declines to about 50% of its initial levels. Signup and view all the answers

What is the main function of the bulbourethral glands during the male sexual response?

To secrete mucous for lubrication Signup and view all the answers

What is the primary consequence of undescended testes if untreated before puberty?

Higher incidence of malignant tumors Signup and view all the answers

Which hormone primarily stimulates the maturation of an egg in the ovary?

Follicle stimulating hormone (FSH) Signup and view all the answers

What physiological change occurs when LH reaches its peak during the menstrual cycle?

Ovulation occurs Signup and view all the answers

Which hormone is primarily responsible for maintaining the uterus lining after egg release?

Progesterone Signup and view all the answers

How does estrogen influence the menstrual cycle after egg maturation?

It inhibits FSH production. Signup and view all the answers

What occurs to the uterine lining during the proliferation phase of the menstrual cycle?

It thickens and becomes more vascular. Signup and view all the answers

What triggers the secretion of luteinising hormone (LH) from the pituitary gland?

Increased levels of estrogen Signup and view all the answers

Which phase of the menstrual cycle is characterized by the buildup of the uterine lining?

Luteal phase Signup and view all the answers

What is the consequence of a failure of testosterone production during fetal life?

Possible cryptorchidism Signup and view all the answers

During which phase does the secretion of progesterone increase significantly?

Luteal phase Signup and view all the answers

Study Notes

Reproductive System Lecture Notes

Topic: Overview of the Reproductive System
Speaker: Dr. Pugazhandhi Bakthavatchalam
Institution: American University of Antigua
Course: Anatomy and Physiology

Learning Outcomes

Students should be able to describe the composition of semen.
Students should be able to describe the physiology of ejaculation.
Students should be able to describe male sex hormones (testosterone) during fetal life, puberty, and adulthood, including regulation and secretion.
Students should be able to describe the female reproductive cycle (ovarian and uterine cycles), including hormonal changes.
Students should be able to describe female sex hormones (estrogen and progesterone) and their regulation.

Sperm Production

Each testis contains approximately 800 seminiferous tubules.
Sperm begin as blob-like cells (spermatogonia).
Sperm pass through stages (primary and secondary spermatocytes) becoming smaller and developing tails (spermatids).
Spermatids mature into sperm with tails.
Thousands of sperm are produced every second, taking about two months to mature.

Sperm Count

Semen (seminal fluid) is more than just sperm.
Sperm accounts for 5-10% of ejaculate.
The remaining 90-95% consists of fructose, fatty acids, and proteins to nourish sperm.
A man produces roughly 525 billion sperm in his lifetime and close to 1 billion per month.
An average ejaculate contains 200-500 million sperm.

Sperm Structure

Sperm consists of a head, midpiece, and tail.
The head contains the nucleus (chromosomes) and acrosome (enzymes for penetrating the egg).
The midpiece contains mitochondria to provide energy for movement.
The tail propels the sperm forward.

Physiology of Erection and Ejaculation

Normal male sexual function requires intact libido, the ability to achieve and maintain penile erection, ejaculation, and detumescence (return to a flaccid state).

Sexual Response Cycle

Excitement Phase: Erection and heightened sexual awareness.
Plateau Phase: Intensified bodily responses (increased heart rate, blood pressure, breathing rate, muscle tension).
Orgasmic Phase: Ejaculation and other responses culminating in sexual excitement.
Resolution Phase: Return to pre-arousal state.

Innervation

Erections are mediated by central (psychogenic) and peripheral (reflexogenic) innervation.
Central innervation (e.g., mental stimulation).
Peripheral innervation (e.g., tactile stimulation).
Tactile stimulation triggers parasympathetic nervous system (PSNS) vasodilation, releasing nitric oxide (NO), inducing vascular smooth muscle relaxation, and blood flow.
Sympathetic nervous system (SNS) inhibition leads to erection.

Erection

A vascular phenomenon involving three cylindrical vascular cords (corpora cavernosa and corpus spongiosum).
Infact blood vessels constrict, allowing inflow, causing rigidity.

Ejaculation

Emission: Mediated by sympathetic nervous system impulses (T11-L2 spinal segments). Contraction of epididymis, ductus deferens, seminal vesicles, and prostate. Internal vesicle sphincter closes, preventing semen from entering the bladder.
Expulsion: Mediated by somatic motor impulses (pudendal nerve). Rhythmic contractions of bulbospongiosus and ischiocavernosus muscles increase pressure in the penis, expelling semen.
Detumescence: Return to flaccid state mediated by norepinephrine (NA) from sympathetic nerves, endothelin from vascular endothelium, and smooth muscle contraction.

Spermatogenesis Maturation and Storage

Sperm maturation occurs within the epididymis (18-24 hours, develops its capability of motility). Inhibitory proteins affect motility until after ejaculation.
Mature sperm stored in the epididymis (most of them)maintain fertility for a month, in an inactive state by substances in the ducts' secretions.
Adult human testes produce up to 120 million sperm daily.

Physiology of Mature Sperm

Mature sperm are motile and capable of fertilizing an ovum in a slightly alkaline medium, becoming inactive in an acidic medium.
Life expectancy in the female genital tract is 1-2 days.

Seminal Vesicle and Prostate Gland Function

Seminal vesicles secrete a mucoid material containing fructose and prostaglandins.
The prostate gland secretes a thin milky fluid containing Ca2+, citrate, phosphate, a clotting enzyme and profibrinolysin, and is important for fertilization success.

Effect of Sperm Count on Fertility

Normal ejaculation volume averages 3-5 ml.
Normal sperm count ranges from 35 to 200 million sperm per ml.
Sperm count below 20 million per ml often leads to infertility.
Sperm morphology and motility are also crucial for fertility; abnormal shapes or lack of motility can cause infertility even with a normal count.
About half the sperm can be abnormal and still be infertile.

Hormonal Factors Stimulating Spermatogenesis

Testosterone: Produced in the interstitial (Leydig) cells of the testes; crucial for growth and division of testicular cells.
Luteinizing Hormone (LH): Secreted by the anterior pituitary; stimulates Leydig cells to produce testosterone.
Follicle-Stimulating Hormone (FSH): Secreted by anterior pituitary; stimulates Sertoli cells, converting spermatids to sperm and crucial for spermatogenesis.
Estrogen: Formed from testosterone; essential for spermatogenesis under FSH stimulation.
Growth Hormone (GH): Necessary for controlling testis metabolic functions; crucial in spermatogonia division. Absence of GH is strongly linked to infertility.

Male Sexual Act

Erection: Parasympathetic impulses from the sacral spinal cord, through pelvic nerves to the penis.
Lubrication: Parasympathetic impulses to urethral and bulbourethral glands to secrete mucus.
Emission: Sympathetic nerves stimulate vas deferens and ampulla. Prostate and seminal vesicles expel their fluids into the internal urethra. Mucous from bulbourethral glands form the semen along with the fluids.
Ejaculation: Increased pressure forces semen out of the urethra.

Testosterone

Secretion: Interstitial (Leydig) cells in the testes.
Male Sex Hormones (Androgens): Testosterone, dihydrotestosterone, and androstenedione.
Testosterone is the most abundant, but dihydrotestosterone is the most active form and found in target cells.
Fetal Development: Stimulates the development of male genitalia, suppresses female genitalia development.
Puberty: Enlargement of secondary sexual characteristics like penis, scrotum, hair and voice changes,.
Adult Life: Maintains characteristics and is responsible for the body's masculine characteristics.

Cryptorchidism

Failure of the testes to descend into the scrotum during fetal life.
Treatment before puberty is crucial due to a higher risk of malignant tumors.

The Menstrual Cycle

The body's way of preparing for pregnancy, controlled by hormones.
Key phases:
- Menstruation: Uterus lining breaks down.
- Proliferation: Uterus lining repairs.
- Ovulation: Release of an egg.
Hormones involved: FSH, LH, estrogen, progesterone.

References

List of textbooks and articles cited.

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Description

This quiz covers key concepts of the reproductive system as discussed in the Anatomy and Physiology lecture by Dr. Pugazhandhi Bakthavatchalam. Students will explore topics such as semen composition, ejaculation physiology, and hormonal regulation in both male and female reproductive cycles.