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What is the primary function of the sperm's head?
What is the primary function of the sperm's head?
At what age does sperm production typically begin?
At what age does sperm production typically begin?
What role do the enzymes in the acrosome play during fertilization?
What role do the enzymes in the acrosome play during fertilization?
Which pathway does the sperm follow during ejaculation?
Which pathway does the sperm follow during ejaculation?
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What is the average sperm count range per mL of semen?
What is the average sperm count range per mL of semen?
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What is the definition of spermatogenesis?
What is the definition of spermatogenesis?
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Where does spermatogenesis take place?
Where does spermatogenesis take place?
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What is the result of meiosis I in spermatogenesis?
What is the result of meiosis I in spermatogenesis?
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What is the chromosomal composition of primary spermatocytes?
What is the chromosomal composition of primary spermatocytes?
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How many sperm cells are produced from one primary spermatocyte after meiosis?
How many sperm cells are produced from one primary spermatocyte after meiosis?
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What role do spermatogonia play in spermatogenesis?
What role do spermatogonia play in spermatogenesis?
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What happens to sperm cells after they form in the seminiferous tubules?
What happens to sperm cells after they form in the seminiferous tubules?
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What is the function of the tunica albuginea in the testes?
What is the function of the tunica albuginea in the testes?
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What characterizes the chromosomes of spermatids?
What characterizes the chromosomes of spermatids?
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What initiates the differentiation of spermatogonia during spermatogenesis?
What initiates the differentiation of spermatogonia during spermatogenesis?
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Sperm production begins at the age of 15 to 18 years.
Sperm production begins at the age of 15 to 18 years.
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The head of the sperm contains a lysosome-like structure called the acrosome.
The head of the sperm contains a lysosome-like structure called the acrosome.
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A sperm cell can survive more than 48 hours in the female reproductive tract after release.
A sperm cell can survive more than 48 hours in the female reproductive tract after release.
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The average sperm count is between 100 to 200 million sperm per mL of semen.
The average sperm count is between 100 to 200 million sperm per mL of semen.
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Only one sperm cell is required to fertilize an egg.
Only one sperm cell is required to fertilize an egg.
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Study Notes
Sperm
- The function of sperm is to move and carry genetic information to the egg
- Sperm production begins at puberty and millions are formed each day in the testes
- Sperm mature at a rate of about 300 million per day and can only survive for 48 hours within the female reproductive tract
- Sperm cells consist of a head, mid-piece and tail
- Sperms mature in the epididymis
Sperm Structure
- The head of the sperm contains DNA (23 chromosomes) which includes 22 autosomes and 1X or 1Y chromosome
- The head also contains a lysosome-like structure called an acrosome which contains enzymes that facilitate penetration of the female egg
- The mid-piece of the sperm cell contains mitochondria which provides the ATP energy for sperm movement
- The wavelike motion of the tail propels the sperm forward
Sperm Count and Fertilization
- The average range of sperm is about 50 to 100 million per mL of semen
- Fertilization is the fusion of egg and sperm to create a zygote
- Sperm travels from the epididymis to the vas deferens and then to the urethra
- 50-500 million sperm are released, but only one sperm cell can enter the egg
- Enzymes help the sperm penetrate the egg, and an instant biochemical change prevents further entry
Spermatogenesis
- Spermatogenesis is the production of sperm cells
- It takes place in the seminiferous tubules
- Spermatogonia are the cells from which sperm cells arise
- Spermatogonia divide by mitosis, with one daughter cell remaining a spermatogonium and the other becoming a primary spermatocyte
Spermatogenesis Process
- Diploid cells are located near the outer wall of the seminiferous tubules
- These cells multiply constantly by mitosis
- About 3 million differentiate into primary spermatocytes each day
- Meiosis I of a primary spermatocyte produces secondary spermatocytes, each with the haploid number of chromosomes
- Meiosis II forms four cells, each with the haploid number of single-chromatid chromosomes
- Each haploid cell differentiates into a sperm cell, which is gradually pushed toward the center of the seminiferous tubule
- From there, the sperm passes into the epididymis, where it matures, becomes motile, and is stored until ejaculation
Puberty
- Puberty is the development of secondary sexual characteristics in males, typically occurring at age 14-15
- Puberty is triggered by increased secretion of Gonadotropin-releasing hormone (GnRH), Follicle-stimulating hormone (FSH), Luteinizing hormone (LH) and testosterone
Physical and Psychological Maturity Changes
- Increase in the rate of production and maturation of sperm
- Enlargement of the testes and penis
- Increased size of the prostate gland, seminal vesicles, and bulbourethral gland
- Enlargement of the larynx and thickening of the vocal cords, resulting in a deeper voice
- Growth of hair on the face, chest, underarms, abdomen, and pubis
- Growth of muscle and bone, and a marked increase in height and weight
Hormonal Control of the Testes
- At puberty, hypothalamic neurosecretory cells increase their secretion of Gonadotropin-releasing hormone (GnRH)
- GnRH stimulates gonadotrophs in the anterior pituitary to increase their secretion of the two gonadotropins, Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH).
- LH stimulates Leydig cells to secrete testosterone
- FSH stimulates spermatogenesis indirectly
Male Infertility
- Infertility is defined as the inability to fertilize a secondary oocyte
- Male infertility occurs when the sperm count falls below 20 million per mL of semen
- Male infertility requires inadequate production of normal sperm count, transportation of sperm through the ducts, and satisfactory deposition in the vagina.
- The main causes of male infertility include X-rays, infections, malnutrition, and significantly higher than normal temperature of the scrotum
Sperm
- Sperm is responsible for carrying genetic information to the egg.
- It's comprised of a head, mid-piece, and tail.
- Production begins at puberty, around 10-14 years of age.
- Millions of sperm are formed daily in the testes.
- Sperm matures in the epididymis.
- Sperm can only survive for 48 hours within the female reproductive tract.
- Head: Contains DNA, which includes 23 chromosomes (22 autosomes + 1X or 1Y).
- Head: Contains the acrosome, a lysosome-like structure with enzymes like hyaluronidase and proteinases aiding in egg penetration.
- Mid-piece: Holds mitochondria to provide ATP for sperm movement.
- Tail: Moves in a wave-like motion to propel the sperm forward.
- Average sperm count: 50 to 100 million per mL of semen.
Fertilization
- Defined as the fusion of the egg and sperm to create a zygote.
- Semen travels via the epididymis, vas deferens, and urethra, typically releasing 50-500 million sperm cells.
- Only one sperm cell reaches the egg.
- Enzymes help the sperm penetrate the egg.
- An immediate biochemical change occurs, preventing other sperm cells from entering.
Spermatogenesis
- Defined as the process of sperm cell production.
- Happens through meiosis, resulting in four haploid sperm cells with 23 chromosomes each.
- Occurs in the testes.
- Spermatogonia are the cells that give rise to sperm.
- Spermatogonia divide by mitosis, with one daughter cell remaining a spermatogonium and the other becoming a primary spermatocyte.
- Diploid cells, found near the outer wall of seminiferous tubules, multiply through mitosis.
- About 3 million diploid cells differentiate into primary spermatocytes daily.
- Primary spermatocytes undergo meiosis.
- Meiosis I of a primary spermatocyte generates secondary spermatocytes, each with a haploid chromosome number (n=23).
- These cells remain in their duplicated state, each containing two identical chromatids.
- Meiosis II produces four cells with a haploid number of single-chromatid chromosomes.
- Each of these haploid cells differentiates into a sperm cell, being pushed towards the center of the seminiferous tubule.
- From there, they move into the epididymis to mature, become motile, and remain stored until ejaculation.
Spermatogenesis Process
- The testes are covered by the tunica albuginea, a connective tissue capsule forming compartments called lobules.
- Each lobule holds one to three convoluted seminiferous tubules where spermatogenesis happens.
- Spermatogenesis begins with spermatogonia.
- Spermatogonia divide to form primary spermatocytes.
- Primary spermatocytes divide to form secondary spermatocytes, which become spermatids.
- Spermatids develop into mature sperm cells (spermatozoa).
- Sertoli cells within the lobules provide nutrients to developing sperm cells.
- Leydig cells produce testosterone, the male sex hormone.
Pathway of Sperm
- Sperm travels through the following path:
- seminiferous tubule
- epididymis
- vas deferens
- ejaculatory duct
- urethra
Puberty
- Occurs around 14-15 years of age in males.
- Marked by the development of secondary sexual characteristics due to increased secretion of:
- Gonadotropin-releasing hormone (GnRH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Testosterone
Puberty: Physical and Psychological Maturity Changes
- Increased production and maturation of sperm in the testes (spermatogenesis).
- Enlargement of testes and penis.
- Increased size of the prostate gland, seminal vesicles, and bulbourethral gland.
- Enlargement of the larynx and vocal cord thickening, resulting in a deeper voice.
- Growth of facial (beard), chest, underarm, abdominal, and pubic hair.
- Muscle and bone growth, leading to increased height and weight.
Hormonal Control of Testes
- At puberty, hypothalamic neurosecretory cells increase gonadotropin-releasing hormone (GnRH) secretion.
- GnRH stimulates gonadotrophs in the anterior pituitary to enhance the release of gonadotropins:
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- LH stimulates Leydig cells (located between seminiferous tubules) to secrete testosterone.
- FSH indirectly stimulates spermatogenesis.
Male Infertility
- Defined as the inability to fertilize a secondary oocyte when sperm count falls below 20 million per mL of semen.
- Male fertility requires adequate sperm production, transportation, and deposition in the vagina.
- Major causes of male infertility include:
- X-rays
- Infections
- Malnutrition
- Abnormally high scrotal temperature.
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Description
Explore the essential aspects of sperm, including its structure, function, and role in fertilization. This quiz covers topics such as sperm production, maturation, and the genetic information it carries. Test your knowledge on the components that enable sperm to successfully fertilize an egg.
