Contents
- Introduction
- Reproduction and Reproductive system
- Functions of the reproductive system
- Reproduction in the various Phyla of the Animal Kingdom
- Oviparity, Viviparity and Ovoviviparity
- Male Reproductive System
- Female Reproductive System
- Sterilization
- Diseases of the Reproductive system
- Summary
- Key Terms
- Recommended Videos
- Test Questions
Learning Objective
By the end of this section, you should be able to:
- Describe reproduction in the animal kingdom.
- Describe the physiology and function of the male reproductive system.
- Describe the physiology and function of the female reproductive system.
Introduction
One of the characteristics of living things that we discussed back in ANP 101 is Reproduction. All living things must be able to produce viable offsprings. Extinction is one of the results of the absence of reproduction, and this has made reproduction to be very essential amongst animals, for continuity of life. We have been seeing in this course, that Animals are organisms composed of various organs and systems; for reproduction to occur, Animals must have organs that perform or dedicate their function towards the reproductive process. The different tissues and organs that are associated with producing an offspring is what we shall be discussing in this section.
Reproduction and Reproductive system
Reproduction is a biological process that deals with the production of offspring(s) that is/are identical to the parent(s). In other words, reproduction involves how an organism makes a copy of itself.
Reproduction can either be sexual (male + female) or asexual (only one parent).
Reproductive system comprises all tissues and organs that play one or more roles towards reproductive function of an organism.
Functions of Reproductive system
The primary function of the Reproductive system is the production of offspring.
There are other secondary functions which is out of our context.
Reproduction in the various Phyla of the Animal Kingdom
Protozoa
Most protozoans reproduce asexually, usually by binary fission (= a parent organism splits into two) and some others, by conjugation (= transfer of genetic materials between two parent organisms).
Sponges
Sponges are sessile (stuck in one place) organisms and most sessile organisms reproduce by budding (= the offspring grows out of the parent). Some sponges can also reproduce by fragmentation (= parent splits and the offsprings regenerate the missing parts).
Cnidarians
We discussed in ANP 101 that cnidarians can either be a Medusae (= free swimming) or a polyp (= sessile, stuck in one place). Medusa reproduce sexually by fusion of male and female gametes while polyps reproduce asexually, mainly by budding.
Flat worms
Many Flatworms are hermaphrodites (= one organism has both male and female reproductive organs). Reproduction is carried out by only one organism which fuses its male gamete and female gamete to form an offspring. Some others (especially the free living ones) are dioecious (= have separate male and female).
Round worms
Most round worms are dioecious and reproduce sexually. Females usually appear longer than males.
Annelids
Annelids reproduce sexually. Many of them (like earthworms) are hermaphroditic while few others have male and female as separate.
Fish, birds, amphibians, mammals, reptiles
All these animals reproduce sexually and their males and females are separate.
Oviparity, Viviparity and Ovoviviparity
Sexual reproduction involves the fusion of female sex gamete (egg) and male sex gamete (sperm) and this is called fertilisation.
Fertilisation in animals, can either be internal (the male deposits sperm inside the female) or external (the female lays eggs and the male fertilises it outside her body). Different animals can either be oviparous, viviparous or ovoviviparous.
Females of oviparous animals are those which lay eggs (examples are fish, hen, snakes). Recently, oviparous animals have further been split into two:
- false oviparous (or ovuliparous), here the female lay unfertilized eggs then the male comes to fertilize it by application of sperm (external fertilization, example: fish);
- true oviparous, here the male mates and deposits sperm into the female, afterwards, the female releases a fertilised egg which will hatch and develop into an offspring (example: hen).
Females of viviparous animals give birth to their offsprings alive (egg is not layed). Fertilisation and several stages of development has taken place inside the female, who, at the end of the day, gives birth to the young one (very much developed) alive. Example: mammals.
Females of ovoviviparous animals lie in between oviparous and viviparous, in the sense that they give birth to their young ones half developed. Young ones are usually given birth to immediately (or just before) the egg hatches, while development and metamorphosis take place outside the mother. Ovoviviparity is not commonly used in recent times and has been replaced with more specific terms.
Now, we're going to be discussing the male and female reproductive systems in higher animals.
Male Reproductive System
The primary function of male reproductive system is the production of sperm and male sexual hormones (such as testosterone). Secondary functions are exhibited during copulation (or sexual activity).
We divide male reproductive system into the external parts (or external genitalia) and internal parts (or internal genitalia).
External genitalia in male reproductive system includes:
Penis - conspicuous, deposits sperm into the genital of female, produce pleasurable sensations during copulation.
Scrotum - flexible flesh behind the penis, which encloses the testes.
Internal genitalia in male reproductive system includes:
Testes - produces sperm.
Epididymis - structure where sperm is stored and fully matures.
Vas deferens or sperm duct - conducts sperm from epididymis to prostrate.
Seminal gland or seminal vesicles - secretes most constituents of semen.
Prostate or Prostate gland - secretes other fluids and important enzymes.
Bulbo-urethral gland - secretes fluid that lubricates tip of penis during sexual activity.
Urethra - conducts semen from prostate to outer part of the penis.
Pathway of Sperm in the Male reproductive system
Sperm is produced in the testes. Afterwards it moves into the epididymis. Sperm mature in the epididymis. During copulation, sperm moves out of the epididymis via the vas deferens, and then along four glands that secrete enzymes and other constituents to make up semen. Sperm finally finds its way to the urethra through which it is released externally.
The four glands (commonly called accessory organs) that secrete enzymes and fluids in the male reproductive tract are seminal glands, ampulla(e), prostate, bulbo-urethral gland.
Testis (plural: testes)
This is commonly known as male's eggs/balls. Usually occur in pair. Testis is the site of production of a male's sperm and the two testes are separated into left and right by a muscle called scrotal septum. Testes optimum temperature for normal function is different from that of the body's, therefore evolution solved the issue by making it to hang externally out of the body, protected and enclosed within the scrotum or scrotal sac (to be discussed later).
Structure of the testes
Seminiferous tubules
Seminiferous tubules are the innermost section of the testes. They are numerous coiled tubules and the actual sites of sperm production. Myoid cells within the seminiferous tubules contract to transport produced sperm out into straight tubules (where seminiferous tubules converge). Seminiferous tubules will be discussed in details below, for now let's move on.
Rete testis
Rete means net. Rete testis is a network of tubules that collect sperm from straight tubules (which generated from seminiferous tubules). In summary, sperm move from seminiferous tubules to straight tubules to rete testis. Rete testis leads the sperm out into the epididymis via efferent ductules.
Septa testis (singular: septum testis)
Septa testis is not to be minced with scrotal septum. Septa testis is a thin sheet of muscle that divides seminiferous tubules into separate individuals or units.
Tunica albuginea (or internal skin)
Tunica albuginea is a tough fibrous tissue that covers the testis. It continues with the septa testis that divides the seminiferous tubules into hundreds of different sections or lobules.
Tunica vaginalis
Tunica vaginalis is the outer covering of the testis after the tunica albuginea. It separates the testis from the scrotal cavity (thin space between the testis and scrotum).
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Scrotum
Scrotum comprises of several sheets of muscle that enclose the testes.
Scrotal cavity
Scrotal cavity is the empty space between the testes and the first sheet of muscle in the scrotum. Scrotal cavity allows for free movement of the testes.
Cremaster
Cremaster is a thick sheet of muscle and the first scrotal covering of the testis just after the scrotal cavity. It contracts and relaxes on the testes. When exposed to cold temperature, it contracts the testes towards the body. It also contract the testes towards the body during copulation.
Dartos muscle
Dartos muscle is another scrotal muscle but it's now on the skin of the scrotum forming a component of the scrotal sac. It is separated from the cremaster by superficial fascia and it encloses both testes which are now separated by a scrotal septum.
Scrotal septum
Scrotal septum is a muscle that separates the two testes into left and right. It is said to originate from a thick lining of muscle on the scrotal surface called the Raphe of Scrotum.
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PRO TIP: animals like whales and elephants lack scrotum. Other animals like few known marsupials have their scrotum in front of their penis as opposed that of general animals.
How is Sperm produced in the Testes | Production of Sperm
Sperm is produced in males' testes by a process called Spermatogenesis.
Spermatogenesis involves three major processes
- Mitosis of spermatogonium
- Meiosis of Spermatocyte
- Spermiogenesis or Maturation of Spermatid
Please if you have no/little knowledge on mitosis and meiosis, go back to ANP 101 page and read on it or you can enter here for mitosis, here for meiosis. You would need to know about them before you proceed. I don't want to be repeating what has already been explained, so this post can be as short as possible.
Mitosis of Spermatogonium
Spermatogonium (plural: spermatogonia) are stem cells found in the seminiferous tubules.
Stem cells contain the same number of chromosomes as other body cells. However, chromosomes of sexual gametes need to be halved (reason for this has been explained in gamete formation).
Stem cells first undergo mitosis to yield two identical stem cells. Out of these two identical stem cells, one will go back to the base of the seminiferous tubule while the other will be used to form sperm. The stem cell that will be used to form sperm is called a primary Spermatocyte.
Meiosis of Spermatocyte
Primary Spermatocyte that has been formed from mitotic division of Spermatogonium still contains the same exact number of chromosomes as all other body cells. Primary Spermatocyte will then undergo meiotic division.
If you recall, meiosis occur in two stages, the first meiotic division of a primary Spermatocyte give rise to two secondary spermatocytes.
The second meiotic division then involves the division of the 2 secondary spermatocytes, to generate 4 spermatids. Each spermatid possesses half number of chromosomes compared to other body cells (= haploid). Several processes occur during meiotic division like crossing over which will alter and shuffle the DNA composition of each Spermatid making each different from one another.
If these look new to you, once again go read on meiosis and gamete formation else you may be going ahead only with half-baked knowledge.
If you have full coverage and you're with me, let's ride on.
Spermiogenesis
Spermiogenesis is the physical maturation of sperm (or spermatids). It involves how spermatids develop from just a cell, into a complex structure that has head, neck and tail. Detailed explanation is not for your level yet, you will get that in higher classes.
Structure of a mature sperm
The primary function of a sperm is to deliver nuclear content to the female gamete. If all sperm in this world were to fertilize one egg each, the world as we know it won't be able to contain the number of babies or young ones that we would have.
Sperm lack most cell organelles, and this is basically to make it small in size and in mass.
Acrosome
Acrosome is an outer membrane, of the head of a sperm (just beneath plasma membrane). It covers the head and contains several enzymes that will be useful for fertilisation.
Head
Head of a sperm encloses the nucleus which contains the DNA or nuclear material of the male.
Neck
The neck of a sperm contain the two centrioles of the original Spermatid (cell that formed sperm). If centrioles look new to you read about it in cell organelles.
The two centrioles arrange each other, with one at the top, and the other beneath. The one beneath forms the microtubule that runs along the tail of the sperm.
Middle piece
Middle piece is stuffed with mitochondria. Mitochondria primarily provide energy for propulsion of the sperm.
Tail (or flagellum)
Tail is the whip-like structure which the sperm uses for movement, swimming or propulsion.
Production and maturation of sperm take place in the seminiferous tubules within the testes and the epididymis.
Seminiferous tubules
Seminiferous tubules are tightly packed, coiled structures within the testes. One seminiferous tubule is separated from the other by septa testis. The wall of Seminiferous tubules are sites of sperm formation. Each seminiferous tubules are in a separate phase of spermatogenesis, this means Spermatogenesis occur independently in each seminiferous tubules.
The spaces between seminiferous tubules contain:
- Areolar tissue
- Blood vessels
- Endocrine cells known as Leydig cells. Leydig cells are responsible for the production of male sex hormones called Androgens, such as testosterone, androstenedione (dominant sex hormones in males, will be discussed later).
Spermatogonia (stem cells), Spermatocytes (undergoing meiosis) and Spermatids (undergoing spermiogenesis) are found in the walls of seminiferous tubules. The nurse cells or Sertoli cells make up the wall of the seminiferous tubules. The nurse cells divide the seminiferous tubules into luminal compartment (towards the lumen-tube space or pipe pathway) and basal compartment (back portion). Spermatogonia are found in the basal compartment, while spermatocytes and spermatids are found in the luminal compartment.
PRO TIP: spermiation is a process in which sperm loses attachment to the nurse cells and enters the lumen of the seminiferous tubules.
Sperm Activation
Sperm that are produced in the seminiferous tubules are physically mature but they cannot move and they are incapable of fertilising an egg. This is where other structures of the male reproductive system come in play. Other structures of male reproductive system are responsible for storage, functional maturation, nourishment, and transport of sperm.
The processes of sperm Activation is called Capacitation and it usually occurs in two stages:
First stage of sperm activation involves the motility of sperm. Sperm's ability to move or swim starts when sperm mixes with other fluids that are produced by the seminal glands, forming semen.
Second stage of sperm activation involves the fertility of sperm. Sperm's ability to fertilize an egg starts when sperm become exposed to the female reproductive tract.
Epididymis
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Epididymis marks the start of the male reproductive tract beyond the seminiferous tubules.
Epididymis is a coiled tube attached to the back (or posterior) of each testis. Sperm is carried from the testis to the epididymis via efferent ductules. Epididymis is the site of sperm's full maturation and storage.
Epididymis is divided into three regions:
- Head (latin - caput): the portion that receive sperm from the efferent ductules.
- Body (latin - corpus): extends down along the surface of the testis.
- Tail (latin - cauda): end portion, number of coils reduce in the tail and it leads to the vas deferens. During long non-sexual periods sperm store here.
Vas deferens / Sperm duct / ductus deferens
Vas deferens transport sperm from the epididymis, out into other portion of the reproductive tract. Vas deferens can also act as site of sperm's storage as it can store sperm for several months in state of suspended animation.
PRO TIP: the end or distal section of vas deferens is always expanded, and this expanded region is called Ampullae (plural: ampulla). Ampulla is one of the four accessory organs in the male reproductive tract.
Seminal glands
Location vary in different animals. It is also called seminal vesicles and its primary function is to secrete seminal fluids: fluids that make up the semen. Semen activates sperm's ability to use its flagellum and swim, and this marks the first step of Capacitation.
Semen: semen is a combination of sperm and seminal fluids. Seminal fluids contain secretions from nurse cells, epididymis, seminal glands, prostate and bulbo-urethral glands. Seminal fluids must maintain alkalinity because semen must be able to withstand female's acidic reproductive tract, else sperm will die.
PRO TIP: many people mistake semen and sperm for the same word, you shouldn't join them in making that mistake, sperm is different from semen. The fluid released by an animal while copulating is semen. One drop of semen contains hundreds to thousands of sperm so technically you can't see sperm.
PRO TIP: ejaculatory duct collect sperm and seminal fluids and deposits them into the urethra in the prostate.
Prostate
The prostate acts like a switch between ejaculation and urination. The structure and location of prostate vary in different animals and it is even absent in some others. Prostate collect semen from the seminal glands, and secretes its own fluid which contain antibiotics that may prevent urinary tract infection in males.
Bulbo-urethral glands
Bulbo-urethral glands are popularly known as Cowper's glands. Bulbo-urethral glands are located along the penis, and they empty their secretions into the urethra. Bulbo-urethral glands secrete thick alkaline mucus which neutralize acids in the urethra and also lubricates the tip of the penis before service.
Urethra
Urethra leads semen onto the outside, and injects semen into the female reproductive tract via the penis.
Penis
Penis is an external genitalia of the male reproductive tract. It carries out two primary functions:
- Convey urine out of the urinary tract.
- Inject semen into the female's vagina during copulation.
Penis is divided into 3 regions:
- Root: the point of attachment of penis to the body is known as root of the penis.
- Body: also called shaft, is the smooth, elastic and tubular portion of the penis.
- Head: also called glans penis, is the sensitive, expanded end, which is the outermost part of a penis. Colour and feel are different from the shaft and it surrounds the external urethral orifice (external end of the urethra).
PRO TIP: some scientists like to include neck of glans among the structure of the penis: the region between the body and the head.
Erection and Erectile tissues of the penis
Erection is necessary for natural insemination and to allow and maintain vaginal penetration.
Erection can be stimulated by erotic thoughts or pre–copulation, and may also occur without sensory interference (as known in male human). During this time of stimulation, sensory nerves in the genital region stimulate the parasympathetic nervous system.
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Acetylcholine is released, which in turn causes the release of Nitrogen Oxide, which diffuses to the smooth muscle of the arteries and act as a vasodilating agent. Arteries then dilate to fill three tissues in the penis, 2 of which are corpora cavernosa (singular: corpus cavernosum) and the third tissue is corpus spongiosum.
These three tissues are the erectile tissues in the penis although they are not found in birds.
Corpora cavernosa are two tubular tissues that run along the length of the shaft of the penis, and they become filled with venous blood during erection.
Corpus spongiosum is a single tubular tissue located just below the corpora cavernosa, and surrounds the urethra. The corpus spongiosum also gets filled with blood, but not like the corpora cavernosa. The corpus spongiosum expands to form the glans penis, which is principally why the head of the penis is usually still malleable during erection, unlike the shaft.
Corpora cavernosa and corpus spongiosum are not found in birds' reproductive tract. Instead, their stimulation results into their cloacal walls getting filled with lymph (not blood). Many birds have no penis (excluding few others), they only press their cloaca against that of the female during copulation.
More so, Protrusion is not usually affected so much by erection in Bulls, because they possess short erectile tissues, but a penis bone (called baculum).
Ejaculation is characterized by involuntary, rhythmic, muscular contractions of an erected penis, which is usually accompanied with discharge of semen and cause pleasurable sensations, known as male orgasm. During ejaculation Bulbocavernosus muscles (at base of the penis) push semen toward external urethral orifice while Ischiocavernosus muscles (along the sides of the penis) stiffen the erect penis.
Hormones of the Male Reproductive system
Recall from our discussion on Endocrine system, Hypothalamus secretes Gonadotropin releasing hormone (GnRH) into the anterior lobe of the pituitary gland. The pituitary gland responds by producing two Gonadotropins which are:
- Luteinizing Hormone (LH): targets the cells that are in the spaces between septa testis, or spaces between seminiferous tubules (known as interstitial cells of the testes). Interstitial cells (especially Leydig cells) secrete testosterone and other androgens (or male sexual hormones). High level of testosterone inhibits release of GnRH.
- Follicle Stimulating Hormone (FSH): targets nurse cells (or Sertoli cells) on the walls of the seminiferous tubules. Spermatogenesis and spermiogenesis occur in the nurse cells. Nurse cells secrete an hormone called androgen-binding proteins (ABP) which stimulates spermiogenesis or Maturation of spermatids.
Functions of testosterone
- Maintains libido (sexual drive) and related behaviors.
- Stimulates bone and muscle growth.
- Establishes and maintains male secondary sexual characteristics.
- Maintains accessory glands and organs of the male reproductive system.
PRO TIP: prostate and external genitalia of male reproductive system respond faster to Dihydrotestosterone (DHT) which is derived from testosterone.
Female Reproductive System
The female reproductive system obviously performs more functions than the male reproductive system: it collects sperm from male, it is the site of fertilization, and it protects, supports and nourishes developing young one.
We divide female reproductive system into external genitalia and internal genitalia.
External genitalia in female reproductive system includes:
Vulva - outermost structure (contains several other tissues).
Cloaca in birds and fishes.
Internal genitalia in female reproductive system includes:
Vagina - where sperm is deposited, birth canal and passageway for menstrual fluids.
Uterus - structure where young one develops.
Uterine tubes (or fallopian tubes) - deliver oocyte and/or embryo to the uterus, it is site of fertilization.
Ovaries - produce female gametes, produce hormones.
PRO TIP: some scientists include the mammary gland(s) which is involved in the production of milk for nourishing young one (this can be found only in mammals).
Ovaries
Ovaries are likened to the testes of the male reproductive system. They perform relatively identical functions. Ovaries are a pair of organs (but single in birds) arranged in opposite sides to each other. Their Primary functions are production of premature egg (oocyte) and secretion of female sex hormones (oestrogen and progesterone).
Layers of the ovaries
Germinal epithelium: outermost tissue that enclose the ovary.
Tunica albuginea: thick tissue below the germinal epithelium, protecting the internals of the ovary.
Internals of the ovary: includes cortex (layer where oocytes are produced) and medulla (innermost layer within the cortex).
Oogenesis
Oogenesis involves the formation and development of oocyte. Processes involved are nearly same as spermatogenesis.
- Mitosis of oogonium
- Meiosis of oocyte
- Maturation of ootid
Mitosis of oogonium
Female stem cells that develop into gametes are called oogonium. An Oogonium undergoes mitosis to form a primary oocyte and another oogonium. This process usually takes place before birth of the female, or immediately after birth of the female.
Meiosis of oocyte
Primary oocytes that result from oogonium begin meiosis 1, but are arrested in Prophase 1 until the animal attains puberty and certain conditions are met. This means that for every female animal, all the oocytes that will produce eggs have been formed during young age.
When a female animal finally reaches puberty, at every specific intervals, primary oocytes are stimulated to complete the meiosis 1 division, to form secondary oocytes. Two secondary oocytes are produced from one primary oocyte, but one (especially the bigger one) gets to develop, while the second becomes a polar body or disintegrates.
This secondary oocyte is released out of the ovary, into the uterine tube where it begins meiosis 2, but again, gets arrested in metaphase 2. Meiosis 2 of the secondary oocyte will not reach completion unless fertilization occurs. If fertilization does not occur, the oocyte will get terminated in some animals or resorbed in others. Once fertilization occurs, the oocyte becomes activated once again and completes meiosis 2 to form one ootid (which will develop into an embryo) and another polar body.
You see the complex processes involved in female reproductive system?
In the next post we shall be discussing well on fertilization.
Structure of the secondary oocyte (unfertilized egg)
Structure of the egg cell in female animals vary in shapes and sizes. Oocytes are usually big enough to be seen, so you don't require a microscope to see them (unlike sperm).
Egg cell is a large cell structure that contains the chromosomes of the female, and is bound by several protective membranes.
Uterine tubes (fallopian tubes)
These are hollow muscular structures that connect the ovaries to the uterus. Oocytes are transported through the uterine tubes by action of ciliary movement and peristaltic contraction of smooth muscle.
Uterus
Uterus is a hollow muscular organ. Uterus provides mechanical protection, nutritional support, and waste removal for embryo and foetus.
The walls of the uterus are:
- Perimetrium (Peri - around): outer surface of the uterus.
- Myometrium (Myo - muscle): thick muscle layer of the uterine wall.
- Endometrium (Endo - inner): glandular inner lining of the uterus, performs major functions in the uterus.
Regions of the uterus
Fundus: rounded portion slightly above the entry of the uterine tubes.
Body: main portion of the uterus.
Cervix: inferior and lower portion of the uterus that projects into the vagina.
Vagina
Vagina is an elastic muscular tube that extends from the cervix to the vestibule. Its diameter vary in different animals because it is highly elastic. Vagina receives penis of the male during copulation, and semen is deposited there. It also holds sperm prior to their entry into the uterus. Vagina is also the outer passage way during birth.
Vestibule
Vestibule is a part of the reproductive tract that is shared with the urinary tract in many animals. It joins the urinary system and the reproductive system out into one vulva (these systems are separated in female humans).
Vulva
Vulva is the external part of the reproductive tract of females. It has sensitive folds of skins and erectile tissue. Swelling and redness of the vulva indicate estrus (heat) detection along with other considered factors.
Hormonal regulation of the female reproductive tract
Similar to that of the males, hypothalamus secretes Gonadotropin releasing hormone (GnRH) into the anterior pituitary gland which in turn secretes Follicle Stimulating hormone (FSH) and produce (not secrete) Luteinizing hormone (LH).
FSH stimulate ovarian follicle development.
As follicles develop, FSH levels decline (negative feedback, read endocrine system to understand more).
Developing follicles secrete oestrogen (especially estradiol) which stimulates secretion of LH.
GnRH stimulates production of LH, but high levels of oestrogen stimulate the secretion of LH.
LH then stimulates the completion of meiosis 1 in primary oocytes which will cause rupture of the follicular walls.
The rupture of follicular walls lead to formation of corpus luteum.
Corpus luteum secretes progesterone.
As progesterone level rises, oestrogen level falls, thereby relaying information back to the hypothalamus to reduce or stop releasing of GnRH.
If pregnancy does not occur, corpus luteum degenerates into Corpus albicans.
When corpus luteum degenerates, progesterone levels fall. This will cause GnRH to increase and a new cycle begins.
PRO TIP: Gestation refers to pregnancy stage and parturition refers to the stage of childbirth.
Sterilization
Sterilization in males (Vasectomy)
This process involves cutting of the sperm duct (vas deferens) to disrupt sexual function and libido. Sperm production is not stopped, however sperm degenerates and are not utilised. Testosterone won't also be available, hence, there will be no libido or sexual drive in the male animal. Vasectomy is sometimes referred to as castration.
Sterilization in females (Tubular Ligation)
Here, the uterine tubes are cut and tied. This occurs less often compared to vasectomy in males, because male animals (especially bulls) are usually employed on farm for work power.
Diseases of the Reproductive system
Prostate Cancer: Abnormal growth of the cells in the prostate. Solved by surgical remove of prostate (prostatectomy) or radiation.
Testicular Cancer: abnormal growth of cells in the testes: rare case.
Breast cancer: Malignant and metastasizing tumor of the mammary glands in female animals.
Ovarian Cancer: benign growth of cells within the ovary.
Cervical Cancer: starts in the cells of cervix and sometimes tumor cells metastasize.
Sexually transmitted diseases/infections
Summary
🐣Reproduction, the ability to give rise to new offsprings, it is one of the primary Characteristics of living things.
🐣Reproduction can either be sexual or asexual.
🐣Asexual Reproduction require only one parent while sexual reproduction require two parents, a male and a female.
🐣A male and female gamete must fuse to give rise to an offspring in sexual reproduction.
🐣The male reproductive system produces sperm.
🐣In ovuliparous animals, female produces egg and lay it, male then comes to pour sperm on it; fertilization of the egg is external.
🐣In true oviparous animals, female reproductive system collects sperm from male, which will internally fertilize its egg, afterwards the fertilized egg is layed, which then develops into an offspring; fertilization of the egg is internal.
🐣In ovoviviparous animals, female reproductive system collects sperm from male, which will fertilize its egg, the fertilized egg is in the reproductive tract until it is just about to hatch or immediately it hatches; fertilization is internal.
🐣In viviparous animals, female reproductive system collects sperm from male which will fertilize its egg, the fertilized egg develops into embryo, grow into a foetus and then a full offspring before it is birthed; fertilization is internal.
🐣Sperm is produced in the male testes and stored in the cauda of the epididymis.
🐣During copulation, sperm passes through the vas deferens, out into the ejaculatory duct where it mixes with fluids from seminal glands and prostate. Sperm then moves to the urethra where it is released during ejaculation.
🐣Female reproductive system produce oocytes, which has not undergone complete division until after it is fertilized.
🐣Internal Fertilisation takes place in the uterine tube (or fallopian tube).
🐣In mammals, embryo moves into the uterus and attaches to the uterine wall until it fully develops.
🐣The male reproductive system and libido is controlled by testosterone and other androgens while the female reproductive system is regulated by oestrogen and progesterone.
Key Terms
Sexual Reproduction • Asexual Reproduction • Oviparity • Ovoviviparity • Ovuliparity • Viviparity • Fertilization • Copulation • Penis • Scrotum • Testes • Epididymis • Vas deferens • Ductus deferens • Sperm duct • Seminal gland • Seminal vesicles • Prostate (gland) • Bulbo-urethral glands • Cowper's glands • Urethra • Seminiferous tubules • Rete testis • Septa testis • Tunica albuginea • Tunica vaginalis • Scrotal Cavity • Cremaster • Dartos muscle • Scrotal Septum • Sperm • Spermatogenesis • Spermatogonium • Spermatocyte • Spermiogenesis • Spermatid • Acrosome • Leydig cells • Testosterone • Androstenedione • Nurse cells • Sertoli cells • Capacitation • Semen • Efferent ductules • Head of epididymis (Caput) • Body of epididymis (Corpus) • Tail of epididymis (Cauda) • Ampulla(e) • Glans penis • Nitrogen Oxide • Corpora cavernosa (corpus cavernosum) • corpus spongiosum • Bulbocavernosus muscles • Ischiocavernosus muscles • External urethral orifice • GnRH • FSH • LH • Libido • Dihydrotestosterone • Vulva • Vagina • Uterus • Uterine tubes • Fallopian tubes • Ovaries • Germinal epithelium • Ovarian cortex • Ovarian medulla • Oogenesis • Oogonium • Oocyte • Ootid • Perimetrium • Myometrium • Endometrium • Cervix • Vestibule • Estrus • Oestrogen • Progesterone • Corpus luteum
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TEST QUESTIONS: REPRODUCTIVE SYSTEM
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TEST QUESTIONS: REPRODUCTIVE SYSTEM
Total Questions: 35
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1. Degeneration of corpus luteum give rise to...
Corpus albicans
2. What is the major role of meiosis during spermatogenesis and oogenesis?
Reduction division to achieve haploid gamete
3. What is the name of the structure that covers the top of the sperm head?
Acrosome
4. The tube that conveys semen from the vas deferens through the penis is known as...
Urethra
5. Which of the following structure is associated with turgidity in the penis and clitoris
Corpus cavernosum
6. Where in the male reproductive system is 'semen' produced?
Testis and epididymis and accessory organs
7. Where in the male reproductive system is 'sperm' produced?
Testis
8. Where in the male reproductive system are 'seminal fluids' produced?
Accessory organs
9. Libido is a result of which of the following?
Testosterone
10. Oogenesis refers to...
Oocyte development
11. An oocyte will normally develop within a follicle and then break free afterwards
True
12. Where exactly does fertilization take place in the female reproductive system?
Fallopian tube
13. What is the role of corpus luteum during pregnancy?
To maintain pregnancy by producing progesterone
14. During pregnancy, which hormone prevents uterine contractions that may result in miscarriage or abortion?
Progesterone
15. Which of these is not an accessory sex gland
Vas deferens
16. Spermatozoa have _ number of chromosomes?
Haploid
17. Major site of sperm storage within the male reproductive tract is...
Cauda
18. _ carry the oocyte
Ovary
19. _ is referred to as the birth canal
Vagina
20. Zona reaction occur when?
After fertilization
21. Castration reduces libido due to lack of supply of...
Testosterone
22. The fallopian tubes transport oocyte from _ to _
Ovary to uterus
23. Which of the following describes the role of zona reaction in reproduction?
Prevention of polyspermy
24. What is the source of nutrition for the embryo before implantation
Yolk sac
25. What is the source of nutrition for the embryo in the first week of implantation
Endometrium
26. The fluid that drips from a male animal's penis prior to service is released by which of these glands?
Cowper's glands
27. Which of these structures in the testis is the site of sperm production?
Seminiferous tubules
28. _ cells in the testis are responsible for secreting testosterone and other androgens
Interstitial cells
29. Straight tubules collect sperm from seminiferous tubules and deliver to
Rete testis
30. Spermatogonium are the stem cells in the testes of male animals and they undergo mitosis to give rise to...
A primary Spermatocyte
31. Sperm detach from the nurse cells on the walls of seminiferous tubules and move into the lumen in a process called...
Spermiation
32. The processes of sperm Activation are referred to as...
Capacitation
33. The body of epididymis is also called?
Corpus
34. When corpus luteum degenerates _ is formed
Corpus albicans
35. In female mammals, which structure of the reproductive tract does foetus grow?
Uterus
Discuss and Explain
1. Identify the structures and functions of the male external genitalia and internal genitalia.
2. Summarize the events of spermatogenesis, and describe the functional anatomy of a mature sperm.
3. Describe the structure and function of the penis.
4. Explain the roles of testosterone and other regulatory hormones in establishing and maintaining male sexual function.
5. Identify the structures and functions of the female external genitalia, internal genitalia.
6. Summarize the hormonal regulation of the female reproductive cycles.
