Male Reproductive System PDF

Reproductive System Male Before we start on the male system, here is a bit of general repro...  Terminology Mitosis (My-toe-sis) Cell division of non-reproductive cells A duplicate copy of the cell is created Meiosis (mei-oh-my) Cell division of reproductive cells Ha...

Reproductive System Male Before we start on the male system, here is a bit of general repro...  Terminology Mitosis (My-toe-sis) Cell division of non-reproductive cells A duplicate copy of the cell is created Meiosis (mei-oh-my) Cell division of reproductive cells Half of the chromosomes of the original cell Gametes – sex cells, have half number of chromosomes Spermatozoa Male gametes Spermatozoon is singular Ovum Female gametes Plural is ova  Terminology Spermatogenesis Creation (genesis) of spermatozoa Beginning at puberty, continues throughout the life of a male Oogenesis Creation (genesis) of ova ready for fertilisation Females have a fixed number of oocytes at birth Oocytes (immature) then become ova (mature) Chromosomes Coiled masses of DNA containing genetic material Found in the nucleus of the cell Gonads – produce gametes (sex cells) Reproductive systems Made up of primary sex organs and accessory sex organs Primary sex organ - Where gametes (sex cells) are made Gonads - testes & ovaries Accessory sex organs - Transport and support gametes and nurture developing embryo Glands and ducts Different species have different accessory sex glands Only body system that requires another individual to fully carry out its function  Functions of Male Reproductive System Produce gametes (sex cells), and deliver to female Produce male sex hormones: Affect libido Influences body shape Enhanced muscle Bone development  Male sex organs Primary sex organs/gonads are the testes Generally oval in size Accessory reproductive organs include: Scrotum Ducts Glands Penis Testes Surrounded by the scrotum – skin layer, usually relatively hairless Made up of: Testis - tubules where testes are made Epididymis – tubules where spermatozoa mature and are stored Spermatic cord = all the structures running to and from the body Contains ductus deferens (tubules that conduct spermatozoa) A large network of blood vessels Cremaster muscle Nerves etc  Testes - Function Function – produce spermatozoa and hormones Spermatozoa – male gametes Three parts – head, midpiece and tail Head (with acrosome) contains enzymes that allow it to penetrate an ovum (female gamete) Midpiece – full of mitochondria, produces the energy for motility Tail – flagellum (cell membrane extension) that creates propulsion Spermatozoa have no food reserves and so have a limited life span - 12-48 hours  Testes - Function Androgens = male sex hormones Testosterone Major androgen Produced in the Interstitial cells (cells of Leydig) that lie in the connective tissue between the seminiferous tubules Testosterone initiates spermatogenesis at puberty and is also responsible for the development of the secondary sex characteristics - growth of reproductive organs, anabolic effects throughout the body and sex drive (libido) In adult males, testosterone is necessary to maintain the normal structure and function of the reproductive organs Testes The reason the testes are on the outside of the body, in the scrotum is to provide a temperature approximately 2-3°C lower than body temperature Lower temperature is important for production of normal spermatozoa Cremaster muscle can pull the testis close to the body in cool temperatures, lower them in hot weather Cremaster muscle  Development of Testes Begin life in abdominal cavity near the caudal pole of the kidneys Scrotal ligament attaches testes to scrotum At or soon after birth, testes are pulled through inguinal ring into the scrotum Spermatic cord contains blood vessels, nerves, cremaster muscle, vas deferens Scrotum consists of skin + vaginal tunics - two layers of connective tissue that surround testes Closed castration 52sec Open Castration 32 sec  Inguinal Ring In the proximomedial thigh (upper middle thigh) Slit-like openings in the abdominal muscles Where blood vessels, spermatic cord, nerves, lymphatic vessels etc enter or leave the abdomen Inguinal hernia (not examined)  Testes – Cryptorchid (not tested) “orchid” = testis “crypt” = hidden When a testis fails to descend, an animal is said to be cryptorchid (“rig” in horses) The cryptorchid testis is usually infertile because of the higher temperatures within the abdomen or inguinal canal (although if just one testis, the other can still be fertile) Still produces sex hormones - behaviour Undescended testes are more likely to develop cancer, so even though they do not produce fertile sperm, it is important that they are removed surgically. Hereditary Testes – Monorchid (not tested) Monorchid Animal only has one testis (the other one is not undescended, it is absent) Rare  Production of Spermatazoa The testis is made up of many coiled tubules surrounded by connective tissue = Seminiferous tubules Spermatozoa are produced in the coiled seminiferous tubules, by the process of spermatogenesis Seminiferous tubules are made up of two types of cells: Germ cells - constantly divide and then migrate toward the lumen of the tubule, where they develop tails and mature to spermatozoa Sertoli cells - support and nourish the germ cells  Duct System Ducts transport spermatozoa from the testes to the exterior 3 parts: Epididymis Vas/ductus deferens (deferent duct) Urethra Epididymis Long, coiled tube on the caudal aspect of the testis Head, body, tail Acts as a storage depot for spermatozoa The head receives immature sperm, and maturation takes place during the journey through the epididymis  Ductus deferens Vas deferens/ductus deferens Vas = vessel Transmits spermatozoa from the testis/epididymis to the urethra It runs up through the inguinal canal into the pelvic cavity, runs down behind the bladder where it passes through the prostate gland to join the urethra Penile Urethra Serves both urinary and reproductive systems Transmits spermatozoa out of the body  Accessory Glands Different species have different accessory sex glands Semen = spermatozoa + seminal fluid (produced by accessory glands) Prostate Gland Gland encircling the urethra just caudal to bladder Produces seminal fluid, activates spermatozoa Present in most mammals Seminal Vesicles Produce seminal fluid Present in rats Not present in cat or dog  Accessory Glands Bulbo-urethral Glands Small glands distal to the prostate Secrete thick mucous that neutralises acidic urine and acts as lubricant Present in cats and stallions Not present in dogs  Penis Delivers semen to female reproductive tract Comprised mainly of muscle, erectile tissue and connective tissue Has an attached root, free shaft and an enlarged tip – glans penis Covered by a fold of skin – prepuce  Penis Entire male cats have spines on the glans of their penis Dogs have a muscular enlargement (bulbis glandis) that becomes engorged with blood during breeding – becomes tightly clamped by contractions of the female’s vagina during copulation Known as the “tie” and lasts for 15-45 minutes after mating Os penis