Flashcards in Test yourself ?s Chpt. 17 The Reproductive System Deck (25)
How does the reproductive system differ from other body systems?
It works to ensure the survival of the species of animal, whereas the other body systems work to ensure the survival of the individual animal.
Why is the reproductive system of an individual animal considered only half a system?
A complete reproductive system is made up of all the male reproductive organs and structures in one animal and all the female reproductive organs and structures in another. Both are necessary for an offspring to be produced.
What is the difference between the diploid chromosome number and the haploid chromosome number? In which body cells is each found?
Each cell in an animal's body (except spermatozoa or ova) contains the same number of chromosomes. The total number of chromosomes in the nucleus of each cell is called the diploid chromosome number.
The number of chromosomes in the reproductive cells must be reduced to half of the diploid number for things to work out, this is called the haploid chromosome number.
So diploid numbers are found in all cells but the reproductive ones and haploids are found in the reproductive ones.
Which reproductive cell, the ovum or the spermatozoon, determines the genetic sex of the offspring when fertilization occurs?
The spermatozoon determines the genetic sex of the offspring, as half of them have an X sex chromosome, and half have a Y sex chromosome.
How does cell division by meiosis differ from cell division by mitosis?
Mitosis: Each of its chromosomes first produces a duplicate copy of itself. When the two daughter cells pull apart, half the chromosomes go to one cell and half go to the other. Each of them ends up with an identical, full diploid set of chromosomes . This ensures that genetic info in all of the body's cells (except for the reproductive cells) stays exactly the same.
Meiosis: The chromosomes do not produce duplicate copies of themselves before the daughter cells pull apart. Half of the total chromosomes (one from each diploid chromosome pair), including one sex chromosome, go to each daughter cell. Genetic material of the reproductive cells gets "shuffled", making unique offspring.
How does spermatogenesis differ from oogenesis? Why are the basic processes so different?
Spermatozoa are produced in the seminiferous tubules of the testes. They are produced continuously and in very large numbers in an effort to ensure that one spermatozoon will successfully reach and fertilize the ovum when breeding occurs.
Spermatogenesis is designed to produce huge numbers of spermatozoa.
Ova are produced in follicles in the ovaries through a process called oogenesis. They are not produced continously like spermatozoa. At or soon after birth, a female has a fixed number of primary oocytes (which are the precursor cells to ova) formed in her ovaries. That is the total number available in her lifetime.
What are the two main functions of the testes? Where in the organ does each take place?
Two main functions: Spermatogenesis and hormone production.
Spermatogenesis takes place in the seminiferous tubules of the testes.
Between the seminiferous tubules, cells called interstitial cells produce male sex hormones, or androgens (the principal androgen being testosterone).
What are the three main part of a spermatozoon? What is the main purpose or function of each?
Three main parts: enlarged head; midpiece; and a long, narrow tail.
Head: contains nucleus of cell and is covered by the acrosome, which contains digestive enzymes. It helps the spermatozoon penetrate through the layers surrounding the ovum to accomplish fertilization.
Midpiece: Power plant of the cell, as it contains many mitochondria arranged in a spiral pattern.
Tail: Resembles a flagellum and contains musclelike fibrils that produce a whiplike movement propelling the cell forward.
Why is a bilaterally cryptorchid animal usually sterile?
The testes retained in the abdominal cavity are usually sterile as the interior of the abdomen is too hot for spermatozoa to be produced.
Would a bilaterally cryptorchid animal exhibit normal male behavior? Why or why not?
Testosterone continues to be produced, despite the testes not having descended, so these animals still have all the characteristics of a male animal but typically cannot reproduce.
What is important about the scrotum's ability to adjust the position of the testes relative to the body?
The scrotum helps to regulate the temperature of the testes. They have to be kept slightly cooler than body temperature to produce spermatozoa. The cremaster muscle attached to the scrotum adjusts the position of the testes relative to the body.
What are the main components of the spermatic cord?
It is a tubelike, connective tissue structure that contains blood vessels, nerves, lymphatic vessels, and the vas deferens.
From what are the visceral and parietal vaginal tunics that cover the testes derived?
The thin, inner layer, the visceral vaginal tunic is derived from the visceral layer of peritoneum that coated the testes as they developed in the abdomen.
The thick, outer layer, the parietal vaginal tunic is derived from the parietal layer of peritoneum that lines the abdominal cavity. It forms a fibrous sac around each testis and spermatic cord.
Where are spermatozoa stored for ejaculation?
The epididymis functions as a storage site for spermatozoa and a place for them to mature before they are expelled by ejaculation. It is a flat, ribbonlike structure that lies along the surface of the testis. It's a single, long very convoluted tube that connects the efferent ducts of the testis with the vas deferens.
Will the volume or gross appearance of the semen of an animal that has had a vasectomy be significantly different from that of a normal animal? Why or why not?
The other components of semen are ejaculated, but no spermatozoa are included as the vasectomy prevents spermatozoa from reaching the urethra during ejaculation.
How does the function of the bulbourethral glands differ from that of the other accessory reproductive glands?
They are located further caudally than the other accessory reproductive glands.
They secrete a mucinous fluid just before ejaculation that clears and lubricates the urethra for the passage of semen.
What are the three main parts of the penis?
The roots, the body, and the glans.
How does the mechanism of erection in animals with a sigmoid flexure in their penis differ from that of other animals?
The nonerect penis of the bull, ram, and boar is normally bent into an S shape. The penises of these animals also have a higher proportion of connective tissue to erectile tissue than other species, and so the penis does not enlarge much when erection occurs.
The main mechanism of erection in these species is a straightening of the sigmoid flexure from internal hydraulic pressure.
The retratcor penis muslce aids with this.
What structures to spermatozoa pass through from their site of production to their eventual deposition in the female productive tract?
1. Seminiferous tubules
2. Efferent ducts of testes
4. Vas deferens (spermatozoa) & accessory reproductive glands (secretions)
6. Female reproductive tract
What two main types of hormones are produced in the ovary? Where is each produced?
Estrogens and progestins
Estrogens are produced by the cells of the developing ovarian follicles and are responsible for the physical and behavioral changes that prepare the animal for breeding and pregnancy.
Progestins, mainly progesterone, are produced by the corpus luteum that develops from the empty follicle after ovulation. Progestins help prepare the uterus for implantation of a fertilized ovum. They are also necessary for pregnancy to be maintained once implantation occurs.
What changes does an ovarian follicle undergo as it develops from a primordial follicle to a mature follicle?
Primordial or primary follicle - reside in this state till activated by the release of FSH (follicle stimulating hormone), then a few start developing
Growing follicle - follicular cells become thickened into cuboidal shapes and begin to multiply; several layers form around the developing oocyte. Estrogen is produced. Fluid-filled spaces begin to form between the cells, these spaces gradually join together, forming one large, fluid-filled space called the antrum.
Mature follicle - reached its full size, looks like a large, blisterlike structure on the surface of the ovary
After ovulation has occured, what cells in the ovary multiply to form the corpus luteum?
The granulosa cells
When ovulation occurs, what causes the ovum to enter the oviduct?
The detached oviducts have to catch the ova in the funnel-like infundibulum, which is the enlarged opening at the ovarian end of each oviduct.
Fimbriae, fingerlike projections along the infundibulum feel along the surface of the ovary and position it where the follicles are located.
When the ovum enters the oviduct after ovulation, delicate muscle contractions and gentle movements of the cilia begin slowly and gently moving it toward the uterus.
Describe the functions of the uterus relating to pregnancy and parturition.
It has to grow along with the developing offspring and then return to its original size after birth.
It forms part of the placenta, which is the life-support system that keeps the fetus alive while it develops during pregnancy. The uterus must remain quiet during pregnancy, and it must contract powerfully at the time of birth. After it has delivered the newborn and the placenta, it has to contract quickly to stop bleeding from the sites where the placenta was attached to its lining.