UNIT B (REPRODUCTION AND DEVELOPMENT) Flashcards
Testes
The male gonads, or primary reproductive organs; male sex hormones and sperm are produced in the testes.
Scrotum
The sac that contains the testes. The temperature in the scrotum is a few degrees cooler than that of the abdominal cavity. The cooler temperatures are important, since sperm will not develop at body temperature. Should the testes fail to descend into the scrotum, the male will not be able to produce viable sperm. This makes the male sterile.
Vas Deferens
Tube that conducts sperm toward the urethra.
Ejaculatory Duct
A tubule formed at the union of the vasa deferentia
and the seminal vesicle ducts and opening into the urethra.
Semen
A secretion of the male reproductive organs
that is composed of sperm and fluids.
Seminal Fluid
The fluid part of semen, which is secreted by three glands.
What contracts during ejaculation?
The vasa deferentia, seminal vesicles, ejaculatory duct, and prostate gland contract, forcing the semen to the base of the penis.
Seminal Vesicle
Structure that contributes to the seminal fluid (semen), a secretion that contains fructose and prostaglandins. Fructose provides a source of energy for the sperm cell and prostaglandins act as a chemical signal in the female system, triggering the rhythmic contraction of smooth muscle and assisting the movement of sperm cells toward the egg.
Prostate Gland
Structure that contributes to the seminal fluid (semen), a secretion containing alkaline buffers that protect sperm cells from the acidic environment of the vagina.
Cowper’s (bulbourethral glands)
Structure that contributes a mucus rich fluid to the seminal fluid (semen).
Ejaculation Order
Seminiferous tubules
Epidydimus
Vas deferens (ductus deferens)
Ejaculatory duct
Nothing
Urethra
Penis
Spermatogenesis Order
Seminiferous tubules: Immature sperm cells divide and differentiate. The site of spermatogenesis.
Spermatogonia: The seminiferous tubules are lined with sperm-producing cells called spermatogonia.
Spermatogonia divide to form Spermacytes
Spermacytes differentiate into Spermatids (23 chromosomes)
Sertoli Cells (Within Seminiferous Tubules)
Nourish the developing sperm cells until they are mature. Produce FSH.
Epididymis
Where sperm cells mature and are stored.
Sperm Order
From each testis, epididymis, ductus deferens, ejaculatory duct, penis.
Acrosome
Sperm have a reduced amount of cytoplasm to help them move fast. Can also be a problem. The cap found on sperm cells, containing enzymes that permit the sperm cell to move through the outer layers that surround the egg.
Middle Piece
Contains mitochondria, energy for the movement of the tail
Tail
Propels the sperm with lashing movement.
Urethra
Carries semen during ejaculation, carries urine from the bladder to the exterior of the body
Primary Sexual Characteristics
Primary sexual characteristics are directly involved in reproduction and are present at birth.
Secondary Sexual Characteristics
External features of an organism that are indicative of its gender (male or female), but are not the reproductive organs themselves.
Distinguishing features, males
Y Chromosome carries the testis-determining factor (TDF) gene to have male sex hormones (androgens). Testes first develop in abdominal cavity and during the 3rd month begin to descend toward scrotum.
Testosterone
Male sex hormone produced by the interstitial cells of
the testes. Stimulates the maturation of the testes and penis and also spermatogenesis. Facial and body hair; the growth of the larynx, which causes the lowering of the voice, the strengthening of muscles. In addition, testosterone increases the secretion of body oils The increased oil production can also create body odour. Testosterone levels are also associated with sex drive and more aggressive behaviour.
Interstitial Cells (Leydig Cells)
Found between the seminiferous tubules within the testes and secrete testosterone.
Gonadotropin-releasing hormone (GnRH)
Chemical messenger from the hypothalamus that stimulates secretions of FSH and LH from the anterior pituitary and regulates the functions of the testes.
Follicle-Stimulating Hormone (FSH) IN MALES
In males, a hormone that increases sperm production. Occurs in the seminiferous tubules (Sertoli Cells).
Inhibin
A hormone produced by the Sertoli cells that inhibits the production of FSH. When sperm counts are high, the Sertoli cells of the seminiferous tubules produce a hormone called inhibin. Inhibin sends a feedback message to the pituitary that inhibits further production of FSH. It also causes the hypothalamus to reduce its production of GnRH.
Luteinizing Hormone (LH)
In males, a hormone that regulates the production of testosterone. Promotes the production of testosterone by the interstitial cells.
High testosterone levels reduce LH production directly by feedback inhibition of LH release from the pituitary and indirectly by feedback inhibition of GnRH release from the hypothalamus. When high levels of testosterone are detected by the hypothalamus, it releases less GnRH, leading to decreased production of LH. Decreased GnRH output, in turn, slows the production and release of LH, which leads to lower testosterone production. Testosterone levels thus remain in check.
Ovum
Egg Cell
Oocyte
An immature ovum
Fetal Development for women
During fetal development in the female, paired ovaries
form in the same abdominal region as the testes in the male. Like the similarly shaped testes, the ovaries descend, but unlike the testes, which come to lie outside of the abdominal cavity, the ovaries remain in the pelvic region. At birth, oocytes (immature ova) are already present within the ovary.
Uterus/Womb
The hollow, pear-shaped organ located between the bladder and the anus in females. The embryo and fetus develop in the uterus during normal pregnancies.
Endometrium
The glandular inner lining of the uterus.
Fallopian Tube (Oviduct0
One of two tubes that connect the ovaries to the uterus. Carries the ovum from ovary to the uterus, and here the beating cilia create a current moving the ovum towards the uterus.
Fibrium
A fingerlike projection at the end of a Fallopian tube.
Vagina
The muscular canal extending from the cervix to the outer environment; the birth canal. The vagina is acidic, creating a hostile environment for microbes that might enter the female reproductive system.
Cervix
A muscular band that separates the vagina from the uterus.
Ovum Size
MUCH larger than sperm! 100 000 times larger, lots of cytoplasm for nutrients.
Oogenesis
The formation and development of mature ova
Follicle
Structure in the ovary that contains the oocyte. A follicle contains two types of cells: a primary oocyte and cells of the granulosa.
Granulosa
The layer of small cells that forms the wall of a follicle. Provides nutrients for the developing oocytes.
Stages of Oogenesis
Nutrient follicle cells surrounding the primary oocyte begin to divide. As the primary oocyte undergoes cell division, the majority of cytoplasm and nutrients move to one of the end poles and form a secondary oocyte. The secondary oocyte contains 23 chromosomes. The remaining cell, referred to as the first polar body,
receives little cytoplasm and dies.
Eventually, the dominant follicle (secondary oocyte) pushes outward, ballooning the outer wall of the ovary. Constriction of blood vessels weakens the ovarian
wall above the follicle, while enzymes weaken the wall of the follicle from the inside. The outer surface of the ovary wall bursts and the secondary oocyte is released. OVULATION!
When Pregnancy Occurs
After ovulation: surrounding follicle cells remain within the ovary and are transformed into the corpus luteum, which secretes hormones essential for pregnancy. If pregnancy does not occur, the corpus luteum degenerates after about 10 days.
Upon its release from the ovary, the secondary oocyte is swept into the funnel-shaped end of the Fallopian tube by the fimbria. The secondary oocyte is moved along the
Fallopian tube by cilia where, if healthy sperm are present, it will become fertilized. The secondary oocyte will then undergo another unequal division of cytoplasm and nutrients and develop into the fertilized ovum. The cell that retains most of the cytoplasm and nutrients becomes the ovum, and the other cell becomes the second polar body, which deteriorates. If the secondary oocyte is not fertilized, it will deteriorate within 24 hours and die. When this occurs, the woman will undergo a menstrual cycle.
Stages of the Ovarian Cycle/Menstrual Cycle
- Flow Phase
- Follicular Stage (Days 6-13)
- Ovulation (Day 14)
- Luteal Phase (Days 15-28)