Reproduction and Development Flashcards
Fertilization:
A single sperm cell fuses with the plasma membrane of the ovum. The head passes into the cytoplasm and causes an electrochemical reaction in the egg. This makes the membrane impermeable to more sperm.
Zygote:
A fused cell that divides many times to form an embryo, then a fetus.
Scrotum:
A sac that regulates the temperature of the testes by contracting the cremaster muscle.
Cremaster muscle when cold:
Contracts to bring testes close to the body to warm up.
Cremaster muscle when warm:
Relaxes to bring testes away from the body.
What is the goal of the cremaster muscle?
To regulate the temperature of the testes 3 degrees Celcius below normal body temperature.
Testes:
Stored in the scrotum. Before birth, they develop in the abdomen and then migrate down a canal into the scrotum around the time of birth.
Seminiferous Tubule:
A sperm-producing organ that appears as tightly coiled tubes. Sperm is produced yet not matured when it leaves the testes and is nourished by Sertoli cells.
Sertoli cells:
Nourishes sperm in the seminiferous tubule.
Interstitial Cells:
The source of the male hormone testosterone. It is scattered between the seminiferous tubules.
What is the problem with sperm being so streamlined?
They only have a small amount of cytoplasm and therefore a limited energy reserve.
The mitochondria of sperm are located between the _________ and the _______.
flagellum, nucleus
Flagellum:
The tail-like structure that propels sperm.
Acrosome:
Caps the head of a sperm cell. It is filled with enzymes that dissolve the outer coating surrounding the egg so that sperm can penetrate it.
A human body cell contains __ chromosomes that are paired together.
46
A human body cell contains __ pairs of chromosomes.
23
Human body cells are called __ploids.
di
A sperm or egg must only contain __ chromosomes to maintain the appropriate chromosome count.
23
Haploid:
Half the normal number of chromosomes.
Spermatogenesis:
The formation of sperm cells which occurs in the testes.
An ejaculation contains ____ _______ sperm.
400 million
Vas Deferens:
A tube that carries sperm from the testes to the urethra. A blockage of the vas deferens will prevent the movement of sperm from the testes to the external environment.
Vasectomy:
A means of birth control.
Ejaculatory Duct:
Propels sperm and semen into the urethra.
What are the steps sperm takes before excretion?
- Epididymus - sperm begins to move and mature
- Vas deferens - carries sperm from the testes to inside the body
- Ejaculatory duct - sperm mixes with ejaculatory fluid
- Urethra - semen leaves the penis
Seminal Vesicle:
Lies below and behind the bladder. Secretes thick, clear fluid into the ejaculatory duct, makes up 60% of semen’s volume.
What is semen made up of?
Fructose and prostaglandins.
Prostaglandins in semen:
Chemical messengers which, once in the female, stimulate uterine peristalsis to help move semen up the uterus.
Fructose in semen:
Energy for the sperm.
Prostate Gland:
The doughnut-shaped gland which surrounds the urethra. It secretes thin milky fluid into the urethra, which makes up 20% of seminal volume. The fluid liquifies the semen, which prevents sperm from clumping together. It is alkaline, which neutralizes acid from residual urine in the urethra and the natural acidity of the vagina.
Cowper’s/Bulbourethral Gland:
A pair of small glands along the urethra, below the prostate. It secretes viscous fluid before the emission of sperm and semen. It is thought to lubricate the penis and vagina and protect sperm from the acidity of the vagina. This is released before ejaculation but may contain some sperm which makes the pullout method ineffective.
Penis:
Made of three cylinders of spongy tissue. Blood fills from the arteries during arousal, and pressure seals off the veins that drain the penis. This leads to an erection.
An erection is parasympathetic/sympathetic.
parasympathetic
Ejaculation is parasympathetic/sympathetic.
sympathetic
Erection:
Erectile tissue (spongiosum) fills with blood which compresses veins and the urethra, which prohibits blood from leaving and urine from entering. A sphincter at the base of the bladder closes as well. Smooth muscle contraction pushes semen out of the urethra.
What factors lead to infertility in men?
Environmental toxins, estrogen in meat and milk, radiation, pesticides, marijuana, alcohol, and constrictive underwear.
What is testosterone’s primary function?
To stimulate spermatogenesis.
What are testosterone’s secondary functions?
Maturation of testes and penis, sex drive, facial/body hair, deeper voice, increased muscle strength, body oil secretion (acne).
In the male reproductive system, the hypothalamus releases what hormone?
Gonadotropin-Releasing Hormone (GnRH)
Gonadotropin-Releasing Hormone (GnRH)
From:
To:
Effect:
From: Hypothalamus
To: Pituitary
Effect: Stimulates pituitary to release LH and FSH.
What two hormones does the anterior pituitary release in the male reproductive system?
Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH).
Follicle-Stimulating Hormone (FSH) MEN
From:
To:
Effect:
From: Anterior pituitary
To: Sertoli cells in the seminiferous tubules
Effect: Stimulates spermatogenesis by the seminiferous tubules
Luteinizing Hormone (LH) MEN
From:
To:
Effect:
From: Anterior pituitary
To: Interstitial cells
Effect: Stimulates testosterone production by interstitial cells. It indirectly stimulates spermatogenesis because testosterone is required for sperm production.
What are the female external genitalia?
Two sets of labia surround the clitoris and vaginal opening.
Ovaries:
Lie in the abdomen below most of the digestive system enclosed in a tough protective capsule. Ovaries produce eggs (follicles) and produce female sex hormones.
An egg cell is called an ___.
ova
A cingular egg cell is called an ____.
ovum
What are the two female sex hormones?
Estrogen and progesterone.
Oogenesis:
Ovaries contain fibrous connective tissue and small groups of cells called follicles. All of the 400,000 follicles a woman will ever have are present at birth. One (very rarely 2) follicle matures and releases its egg during each menstrual cycle.
Of the 400,000 follicles a woman has, how many will a woman release?
Only a few hundred.
What are the two types of cells follicles are composed of?
Primary oocyte and granulosa cells.
Oocyte contains __ chromosomes and undergoes (meiosis/mitosis).
46, meoisis
What is a mature oocyte called?
An ovum.
What provides nutrients for an oocyte?
Granulosa cells.