Term
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Definition
Meiosis is a two-part cell division process in organisms that sexually reproduce.
Meiosis produces gametes with one half the number of chromosomes as the parent cell.
There are two stages of meiosis: meiosis I and meiosis II. At the end of the meiotic process, four daughter cells are produced.
Each of the resulting daughter cells has one half of the number of chromosomes as the parent cell.
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Term
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Definition
Before a dividing cell enters meiosis, it undergoes a period of growth called interphase. Interphase:
- G1 phase: The period prior to the synthesis of DNA. In this phase, the cell increases in mass in preparation for cell division. Note that the G in G1 represents gap and the 1 represents first, so the G1 phase is the first gap phase.
- S phase: The period during which DNA is synthesized. In most cells, there is a narrow window of time during which DNA is synthesized. Note that the S represents synthesis.
- G2 phase: The period after DNA synthesis has occurred but prior to the start of prophase. The cell synthesizes proteins and continues to increase in size. Note that the G in G2 represents gap and the 2 represents second, so the G2 phase is the second gap phase.
- In the latter part of interphase, the cell still has nucleoli present.
- The nucleus is bounded by a nuclear envelope and the cell's chromosomes have duplicated but are in the form of chromatin.
- In animal cells, two pair of centrioles formed from the replication of one pair are located outside of the nucleus.
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Term
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Definition
Prophase I:
- Chromosomes condense and attach to the nuclear envelope.
- Synapsis occurs (a pair of homologous chromosomes lines up closely together) and a tetrad is formed. Each tetrad is composed of four chromatids.
- Crossing over may occur.
- Chromosomes thicken and detach from the nuclear envelope.
- Similar to mitosis, the centrioles migrate away from one another and both the nuclear envelope and nucleoli break down.
- Likewise, the chromosomes begin their migration to the metaphase plate.
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Definition
Metaphase I:
- Tetrads align at the metaphase plate.
- Note that the centromeres of homologous chromosomes are oriented toward the opposite cell poles.
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Term
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Definition
Meiosis Study Guide
- Overview
- Stages of Meiosis
- Meiosis Diagrams
- Glossary of Terms
- Quiz
Anaphase I:
- Chromosomes move to the opposite cell poles. Similar to mitosis, the microtubules and the kinetochore fibers interact to cause the movement.
- Unlike in mitosis, the homologous chromosomes move to opposite poles yet the sister chromatids remain together.
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Term
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Definition
Telophase I:
- The spindles continue to move the homologous chromosomes to the poles.
- Once movement is complete, each pole has a haploid number of chromosomes.
- In most cases, cytokinesis occurs at the same time as telophase I.
- At the end of telophase I and cytokinesis, two daughter cells are produced, each with one half the number of chromosomes of the original parent cell.
- Depending on the kind of cell, various processes occur in preparation for meiosis II. There is however a constant: The genetic material does not replicate again.
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Term
| What is the function of the testis? |
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Definition
The testes are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord. Most men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubules are responsible for producing the sperm cells through a process called spermatogenesis.
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Term
| What is the function of the epididymis? |
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Definition
| The epididymis is a long, coiled tube that rests on the backside of each testicle. It functions in the transport and storage of the sperm cells that are produced in the testes. It also is the job of the epididymis to bring the sperm to maturity, since the sperm that emerge from the testes are immature and incapable of fertilization. During sexual arousal, contractions force the sperm into the vas deferens. |
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Term
| What is the function of the ductus deferens? |
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Definition
| The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports mature sperm to the urethra in preparation for ejaculation. |
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Term
| What is the function of the ejaculatory duct? |
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Definition
| ejaculatory duct, either of two hollow tubes, each formed by union of the ampulla of a ductus deferens and the excretory duct of a seminal vesicle. The ducts, which open into the urethra about halfway through the prostate gland, function to mix the sperm stored in the ampulla with fluids secreted by the seminal vesicles and to transport these substances to the prostate. |
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Term
| What is the function of the urethra? |
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Definition
| The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of expelling (ejaculating) semen when the man reaches orgasm. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm. |
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Term
| What is the function of the penis? |
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Definition
| The penis is the male organ for sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped end of the penis. The glans, which also is called the head of the penis, is covered with a loose layer of skin called foreskin. (This skin is sometimes removed in a procedure called circumcision.) The opening of the urethra, the tube that transports semen and urine, is at the tip of the glans penis. The penis also contains a number of sensitive nerve endings. |
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Term
| What is the function of the seminal vesicles? |
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Definition
| The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy and helps with the sperms’ motility (ability to move). The fluid of the seminal vesicles makes up most of the volume of a man’s ejaculatory fluid, or ejaculate. |
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Term
| What is the function of the bulbourethral glands? |
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Definition
| The bulbourethral glands, or Cowper’s glands, are pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra. |
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Term
| What is the function of the prostate gland? |
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Definition
| The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra, which carries the ejaculate to be expelled during orgasm, runs through the center of the prostate gland. |
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Term
| Trace the pathway of sperm outside the body. |
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Definition
| seminiferous tubules of testes -> epididymis -> vas deferens -> prostate -> urethra |
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Term
Why are the testes in the scrotum rather than inside the abdominopelvic cavity?
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Definition
| The function of the scrotum appears to be to keep the testes at a temperature slightly lower than that of the rest of the body.[2] For human beings, the temperature should be one or two degrees Celsius below body temperature (around 37 degrees Celsius or 99 degrees Fahrenheit); higher temperatures may be damaging to sperm count. The temperature is controlled by the scrotum moving the testicles closer to the abdomen when the ambient temperature is cold, and further away when it is hot. |
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Term
What is the importance of interstitial (Leydig) cells?
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Definition
| Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH). Leydig cells are polyhedral in shape, display a large prominent nucleus, an eosinophilic cytoplasm and numerous lipid-filled vesicles. |
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Term
| Name the erectile tissue of the penis. |
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Definition
In the penis, and in the clitoris, erectile tissue is the corpora cavernosa. This is soft tissue that has a texture like a sponge. It becomes filled with blood, and swells, which causes the penis to expand and become stiff and erect.
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Term
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Definition
Spermatogenesis is the development of mature spermatozoa (sperm cells) from spermatogonia; it includes spermatocytogenesis and spermiogenesis.
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Term
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Definition
A cell produced at an early stage in the formation of spermatozoa, formed in the wall of a seminiferous tubule and giving rise by mitosis to spermatocytes
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Term
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Definition
A cell produced at the second stage in the formation of spermatozoa, formed from a spermatogonium and dividing by meiosis into spermatids
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Term
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Definition
The spermatid is the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte.
Spermatids are connected together by cytoplasmic material and have superfluous cytoplasmic material around their nuclei.
When formed, early round spermatids must undergo further maturational events in order to develop into spermatozoa, a process termed spermiogenesis (also termed spermeteliosis).
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Term
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Definition
| The term sperm is derived from the Greek word (σπέρμα) sperma (meaning "seed") and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell. The human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the female egg to form a diploid cell. |
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Term
Describe the steps from spermatogonia à sperm.
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Definition
Spermatogonium,
spermatocytes (primary then secondary),
spermatid
spermatozoan
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Term
What are the 3 main regions of the sperm?
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Definition
Each sperm cell has three parts: a head, middle piece, and tail. An acrosome at the head tip produces enzymes that help penetrate the female ovum (egg). During conception, chromosomes (genetic material) in the nucleus (cell control center) join with chromosomes in the ovum. The middle piece contains mitochondria, structures that provide energy for the sperm. The mitochondria are tightly spiraled around the axial filaments (contractile portion) of the flagellum (tail). Centrioles form the tail, which moves the sperm toward the ovum. An ejaculation (ejection of sperm from the penis) has 300 to 500 million sperm.
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Term
What are the components & hormones involved in the HPG axis in males & females?
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Definition
1.Hypothalamus releases gonadotropin-releasing hormone (GnRH)
2.GnRH stimulates anterior pituitary to secrete FSH & LH
3.FSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosterone
4.LH stimulates interstitial cells to release testosterone
5.Testosterone is final trigger for spermatogenesis
6.Feedback inhibition on hypothalamus & pituitary results from:
•Rising levels of testosterone
•Inhibin (released when sperm count is high) |
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Term
What are some functions of testosterone in males?
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Definition
Testosterone is the major sex hormone in males and plays a number of important roles, such as:
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The development of the penis and testes
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The deepening of the voice during puberty
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The appearance of facial and pubic hair starting at puberty; later in life, it may play a role in balding
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Muscle size and strength
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Bone growth and strength
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Sex drive (libido)
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Sperm production
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Term
| What is the function of the ovaries? |
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Definition
•Produce female gametes (ova)
•Secrete female sex hormones (estrogen & progesterone)
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Term
| What is the function of the oviducts? |
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Definition
Transmission the egg from the ovary to the uterus.
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Term
| What is the function of the uterus? |
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Definition
The uterus (from the Latin, meaning "womb") is an inverted, pear-shaped structure located between the urinary bladder and the rectum. Implantation of a fertilized ovum occurs in the uterus. Following implantation, the uterus houses, nourishes, and protects the developing fetus during pregnancy.
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Term
| What is the function of the vagina? |
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Definition
The vagina is the female sex organ. It receives the male penis during sexual intercourse, provides the passageway for menstrual blood during menstruation, and serves as the birth canal for fetal offspring.
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Term
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Definition
| Ovarian follicles are the basic units of female reproductive biology, each of which is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte (immature ovum or egg). These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single competent oocyte in humans. These eggs/ova are only developed once every menstrual cycle (e.g. once a month in humans). |
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Term
Describe what happens from primordial follicle à corpus luteum in the ovary.
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Definition
•Primordial follicle: 1 layer follicle cells + oocyte
•Primary follicle: 1 layer cuboidal or columnar follicle cells + oocyte
•Secondary follicle: 2+ layers of granulosa cells + oocyte
•Late secondary follicle: contains fluid-filled space between granulosa cells; form a central antrum
•Vesicular (Graafian) follicle - fluid-filled antrum forms; follicle bulges from ovary surface
•Ovulation - ejection of oocyte from ripening follicle
•Corpus luteum develops from ruptured follicle after ovulation
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Term
Where does most fertilization take place in the female reproductive tract?
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Definition
human egg is fertilized by a human sperm in the fallopian tubes of the female. The fallopian tubes are the passageway between the ovaries and the uterus.
After fertilization, the developing baby travels down the tubes into the uterus where it will implant into the wall of uterus, establishing a source of nourishment for the duration of the pregnancy.
In rare cases, the baby will not travel to the uterus and attempts to implant within the fallopian tubes, resulting in an ectopic pregnancy. These pregnancies often result in miscarriage and occasionally must be aborted to save the life of the mother. In even more rare situations, the ectopic pregnancy will later dislodge and travel to the uterus and progress normally
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Term
Name some functions of mucus in the female reproductive tract.
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Definition
| In the female reproductive system, cervical mucus prevents infection. The consistency of cervical mucus varies depending on the stage of a woman's menstrual cycle. At ovulation cervical mucus is clear, runny, and conducive to sperm; post-ovulation, mucus becomes thicker and is more likely to block sperm.[c |
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Term
Contrast stratum functionalis & stratum basalis.
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Definition
| They’re both part of the endometrium. The stratum functionalis is shed each month while the stratum basalis is a permanent layer. |
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Term
· What layer of the uterine wall is influenced by oxytocin?
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Definition
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Term
· Name the external genitalia of females.
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Definition
The external female genitalia (vulva) include:
- The opening of the vagina (also called the birth canal). The vagina is part of the reproductive tract and extends from the womb (uterus) to outside the body.
- The fleshy lips (labia majora and labia minora) around the vagina.
- A small bump of tissue (clitoris) covered with a thin flap of tissue. The clitoris is the main source of sensations during sexual activity.
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Term
| Importance of mammary glands |
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Definition
•Important in the production of milk
•Modified sweat glands consisting of 15–25 lobes
•Lobes contain glandular alveoli that produce milk and pass it into lactiferous ducts: lactiferous ducts ® lactiferous sinuses ® open to the outside at the nipple
•Areola: pigmented skin surrounding nipple
•Suspensory ligaments: attach breast to underlying muscle
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Term
· Describe the risk factors, detection, & treatment methods for breast cancer.
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Definition
Risk Factors: •Early onset of menstruation & late menopause
•No pregnancies or first pregnancy late in life
•Family history of breast cancer
•10% are due to hereditary defects, including mutations BRCA1 & BRCA2 genes. 70% have no known risk factor.
Detection: •Early detection via self-examination & mammography
Treatments: •Radiation, chemotherapy, & surgery followed by irradiation & chemotherapy
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Term
| How is oogenesis different than the male's spermatogenesis? |
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Definition
spermatogenesis takes place in the testes of males, oogenesis takes place in the ovary of the females.
Spermatogenesis produces small, motile spermatozoa whereas in oogenesis the ovum is spherical, not motile and is much larger with more food reserves and cytoplasm.
Spermatogenesis involves a metamorphosis stage called spermiogenesis, in oogenesis there is no metamorphosis stage.
In spermatogenesis, 4 gametes are produced from each meiotic division, whereas in oogenesis there is only 1 gamete produced from each division as the unequal cytokinesis leads to the formation of polar bodies.
Spermatogenesis occurs in males (human males) continuously from puberty to death whereas oogenesis starts in females at puberty and then occurs on a monthly basis until the menopause. It takes 70 days for sperm to be produced in males.
In oogenesis, the development of the oocyte is arrested at prophase I of meiosis until puberty, and then stops at metaphase II of meiosis until fertilisation, where the meiotic division is finally completed. In males meiosis occurs continuously
The hormones in the 2 processes have different effects - in oogenesis, FSH is responsible for the choice of the primary oocyte and causes the cells of the membrana granulosa to proliferate to form the theca interna which secretes oestrogen, and the theca externa. LH in females stimulates ovulation and the maturation of the Graafian follicle. In males, on the other hand, FSH increases the activity of the Sertoli cells which are involved in spermiogenesis (the metamorphosis stage of spermatogenesis). LH in males stimulates the Leydig cells to secrete testosterone.
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Term
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Definition
| Oogenesis is the production of an ovum or egg cell, the female gamete or sex cell. It is one type of gametogenesis, or sex cell production, the other being the male process of spermatogenesis. Oogenesis happens in all sexually reproductive species. It includes all of the immature stages of the ovum. As it matures, the ovum passes through five stages in mammals: the oogonium, the primary oocyte, the secondary oocyte, the ootid, and the ovum. |
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Term
What are the 2 main phases of the ovarian cycle? When is ovulation? What is ovulation?
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Definition
As a rule, the ovarian cycle lasts 28 days. It is subdivided into two phases:
- Follicle phase: recruitment of a so-called follicle cohort and, within this, the selection of the mature follicle. This phase ends with ovulation. Estradiol is the steering hormone. Normally, it lasts 14 days, but this can vary considerably!
- Luteal phase: progesteron production by the "yellow body" (= corpus luteum) and lasts 14 days (relatively constant).
Ovulation begins on the 14th day.
the expulsion of an ovum from the ovary (usually midway in the menstrual cycle)
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Term
· What are the 3 parts of the uterine cycle? What happens in each?
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Definition
1. Menstrual phase
•Ovarian hormones are at lowest levels
•Gonadotropins are beginning to rise
•Stratum functionalis is shed & menstrual flow occurs
2. Proliferative phase
•Estrogen levels prompt generation of new functional layer & increased synthesis of progesterone receptors in endometrium
3. Secretory phase
•Progesterone levels prompt:
•Further development of endometrium
•Glandular secretion of glycogen
•Formation of cervical mucus plug
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Term
· Why is the corpus luteum important?
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Definition
| In the ovaries the female egg develops in a follicle, when the egg is shed the remaining follicle is called corpus luteum from latin yellow body, it is important for pregnancybecause this corpus luteum produces a hormone progesterone which is needed to mmaintainpregnancy as progesterone causes the lining of the uterus to become thicker and full of blood vessles ready for the zygote to embedd in if fertilization occurs. |
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Term
| What are some functions of estrogen in females? |
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Definition
•Increased estrogen levels:
•Promote oogenesis & follicle growth in ovary
•Exert anabolic effects on female reproductive tract
•Support rapid growth spurt at puberty
•Induce secondary sex characteristics:
•Growth of breasts
•Increased deposit of subcutaneous fat (hips & breasts)
•Widening & lightening of pelvis
•Metabolic effects
•Maintain low total blood cholesterol & high HDL levels
Facilitates calcium uptake
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Term
| What are some effects of progesterone? |
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Definition
•Progesterone works with estrogen to establish & regulate uterine cycle
•Effects of placental progesterone during pregnancy
•Inhibits uterine motility
•Helps prepare breasts for lactation
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Term
· What is the sexually indifferent stage in human development?
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Definition
Before week 5.
•Gonads begin development in 5th week as gonadal ridges
•Primordial germ cells go to gonadal ridges to provide germ (stem) cells destined to become spermatogonia or oogonia
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Term
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Definition
•In response to rising levels of gonadal hormones:
•Reproductive organs grow to adult size & become functional
•Secondary sex characteristics appear
•Earliest time that reproduction is possible
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Term
| What are the differences between male and female puberty? |
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Definition
Two of the most significant differences between puberty in girls and puberty in boys are the age at which it begins, and the major sex steroids involved.
Although there is a wide range of normal ages, girls typically begin the process of puberty at age 10 or 11; boys at age 12 or 13.[1][2] Girls usually complete puberty by ages 15–17,[2][3][4] while boys usually complete puberty by ages 16–18.[2][3][5] Any increase in height beyond the post-pubertal age is uncommon. Girls attain reproductive maturity about 4 years after the first physical changes of puberty appear.[4] In contrast, boys accelerate more slowly but continue to grow for about 6 years after the first visible pubertal changes.[6]
For boys, an androgen called testosterone is the principal sex hormone. While testosterone produces all boys' changes characterized as virilization, a substantial product of testosterone metabolism in males is estradiol, though levels rise later and more slowly than in girls. The male "growth spurt" also begins later, accelerates more slowly, and lasts longer before the epiphyses fuse. Although boys are on average 2 cm shorter than girls before puberty begins, adult men are on average about 13 cm (5.2 inches) taller than women. Most of this sex difference in adult heights is attributable to a later onset of the growth spurt and a slower progression to completion, a direct result of the later rise and lower adult male levels of estradiol.[7]
The hormone that dominates female development is an estrogen called estradiol. While estradiol promotes growth of breasts and uterus, it is also the principal hormone driving the pubertal growth spurt and epiphyseal maturation and closure.[8] Estradiol levels rise earlier and reach higher levels in women than in men.
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Term
· What is menopause? What are the differences for males & females?
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Definition
•Has occurred when menses have ceased for an entire year
•Declining estrogen levels ®
•Atrophy of reproductive organs & breasts
•Irritability & depression in some
•Hot flashes as skin blood vessels undergo intense vasodilation
•Gradual thinning of skin & bone loss
•Increased total blood cholesterol levels & falling HDL
•There is no equivalent to menopause in males
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Term
| What are 2 primary functions of the reproductive system? |
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Definition
Within the context of producing offspring, the reproductive system has four functions:
- To produce ova (eggs) and sperm cells
- To transport and sustain these cells
- To nurture the developing offspring
- To produce hormones
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Term
| The differences between Meiosis 1 and 2? |
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Definition
In the beginning, before any Meiosis occurs, centromeres in the cell holds double-stranded chromosomes together. So, there are two double-stranded chromosomes.
In Meiosis I, the cell undergoes prophase, metaphase, anaphase, and finally telephase, causing the cell to divide into two, each with one double-stranded chromosome.
Meiosis II is simply the second division of Meiosis I, splitting the cell once again. This results in four cells with one-stranded chromosomes.
the difference between them is when they come in during Meiosis. |
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