16.2 Reproductive System - Male

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Reproductive Systems:

Reproductive Systems Female Reproductive System Male Reproductive System General Training Module RK

Reproductive Systems:

Reproductive Systems Introduction to reproduction Part A : T he Female Reproductive System Part B : The Male Reproductive System Anatomy of the Male Reproductive S ystem Function of the Male Reproductive System Endocrine Function of the Male Reproductive system Puberty and Secondary Sexual Characteristics Sperm, Semen and Spermatogenesis Erection, Ejaculation & Sexual I ntercourse

Reproduction:

Reproduction The ability to reproduce is a key feature of all living things that differentiate them from the non-living. It helps the continuation of the species. The more primitive the animal simpler the reproductive process. In simpler organisms reproduction is asexual (like binary fission seen in bacteria which is unicellular – that has only one cell) That is they do not have male and female forms among them. All of them are the same and they reproduce by dividing the cell into two and becoming two cells

Reproduction:

Reproduction In humans the reproduction is sexual. It is achieved through the union of male and female cells specially formed for reproduction within each male and female body. The union of these two cells is accomplished under natural conditions through sexual intercourse. The males and females are different anatomically and physiologically in a way that help them to fulfill their reproductive roles

Reproduction:

Reproduction The cells formed within our bodies for reproductive purpose are called germ cells or gametes. In the male these are spermatozoa, more commonly known as sperm (Colloquially called seeds) – produce in the testes In the female they are ova (Colloquially called eggs) – produced in the ovaries

Reproduction:

Reproduction How do the sperm and ova differ from normal cells? Each cell has what we call genetic material made up of DNA – Deoxy -Ribose Nucleic Acid They are large organic molecules located in the nucleus of the cell. They have the instructions for the synthesis of functional and structural components of cells and cellular processes in order to grow and develop the organism and then sustain life.

Reproduction:

Reproduction DNA within the nuclei are arranged into structures known as chromosomes Each human body cell nucleus has 23 pairs of chromosomes (46 in total) that contains the DNA required for human life. One chromosome in each pair is received from the mother and the other from the father Reproductive cells or gametes are special in that way they only have 23 chromosomes (not pairs) These are formed from a different type of cell division called MEIOSIS in the reproductive organs. So that when they unite through reproduction the new cell formed has the usual 23 pairs (46) of chromosomes

Reproduction:

Reproduction The function of the male reproductive organ is therefore to produce sperms and transmit them to the female reproductive system where they unite with the ova. This is called FERTILIZATION and the new cell formed is called the ZYGOTE The function of the female reproductive system therefore is to produce ova, receive the sperm, accomplish fertilization. In addition the female reproductive organ also provides the template for the zygote to implant and grow, nurture and protect the growing embryo/fetus until birth. Thereafter it produces nutrition to the young infant through lactation (breast milk) until it can take other forms of food.

Male Reproductive System:

Male Reproductive System

Male Reproductive System:

Male Reproductive System The male reproductive system consists of external genitalia (the Penis and the scrotum) and other internal organs: The Scrotum: has the testes(2) and the epididymides (2) Ductus deferens (2) (Vas deferens) Spermatic cords (2) Seminal vesicles (2) Ejaculatory ducts (2) Prostate Gland (1) The Penis and urethra (1)

The Male Reproductive System:

The Male Reproductive System

Scrotum:

Scrotum It is divided into two compartments each with one testes, epididymis and the testicular end of the spermatic cord Lies below the pubic symphysis , in front of the upper part of the thighs behind the penis This way the testes lies outside the body in a temperature lower than body temperature which is needed for succussful formation of sperm Is a pouch of deeply pigmented skin, connective tissue and smooth muscle

Testes:

Testes They are the reproductive glands of the male Lie suspended in the scrotum on each side by the spermatic cord During the fetal life testes at first develop in the abdominal cavity just below the kidneys They subsequently descend (8 th month) to the scrotum to take up their position in adults Sometimes infants are born with un-descended testes (empty scrotum)

Testes:

Testes Each testes is covered with what was originally the peritoneum of the abdomen. Inside of each testes is divided into 200 to 300 lobules. Inside each lobule are 1 to 4 convoluted loops called SEMNIFEROUS TUBULES They are lined by germinal epithelial cells It is here the sperm is first produced

Testes:

Testes At the upper pole of the testes each seminiferous tubule converge to form a single tortuous tubule called the Epididymis This tubule continues as the vas or ductus deferens and leaves the scrotum in the spermatic cord along with blood and lymph vessels of the scrotum Between Seminiferous tubules are interstitial cells of Leydig that secrete the hormone testosterone

Spermatic Cord:

Spermatic Cord There two – one leading from each testes on either side. Each has enclosed in a sheath of fibrous tissue and smooth muscles: Ductus (Vas) deferens Testicular artery and venous plexus Lymphatics Nerves (T10 & T11) They pass upwards in the inguinal canal to the pelvic cavity At the deep ring of the canal the Ductus Deferens ascend medially and posteriorly to the posterior wall of the bladder arching over the ureter carrying the sperm with them.

Inguinal Canal:

The  inguinal canal  is a passage in the anterior abdominal wall that in men conveys the spermatic cord and in women the round ligament of uterus. The  inguinal canal  is larger and more prominent in men. There is one  inguinal canal  on each side of the midline. Inguinal Canal

Seminal Vesicles:

Seminal Vesicles Seminal vesicles are two small fibro- muscluar pouches that on either side of the midline behind the bladder close to its posterior wall. Their short ducts join with the ductus deferens on either side to form the ejaculatory duct on each side Seminal Vesicles secrete a fluid that provides nourishment to the sperm and keep them alive

Ejaculatory Ducts:

Ejaculatory Ducts Ejaculatory ducts pass through the prostate and enters the prostatic part of the urethra within the prostate. This way the sperm and the seminal fluid of the two seminal vesicles are transported to urethra

Prostate Gland:

Prostate Gland prostate Gland lies in the pelvic cavity in front of the rectum and behind the pubic symphysis surrounding the first part of the urethra extending from the bladder neck/internal sphincter above to the external urethral sphincter below. It has several lobes: anterior lobe (no glands), posterior lobe, two lateral lobes (largest) and a median lobe in the upper part in between the ejaculatory ducts and the urethra It has a outer fibrous covering, smooth muscle and glandular columnar epithelial cells It secretes a thin lubricating fluid that passed into the urethra through numerous openings – part of the fluid of semen

Prostate Gland:

Prostate Gland

Urethra:

Urethra The male urethra is about 20 cm and has three parts : Prostatic urethra – the first part The membranous urethra – the narrowest and shortest, from the prostate to the bulb of the penis after passing through the perineal membrane Spongiose urethra – lies within the corpus spongiosum of the penis, extends up to the external urethral orifice in the glans penis where it opens to the exterior It carries both urine and semen in men

Penis:

Penis Externally the penis has a shaft and a head ( Glans ) The head is covered by a skin fold that in the adult can be retracted backwards (foreskin or prepuce) At the tip of the head is the opening of the urethra

Penis:

Penis The shaft of the penis is made of three masses of ‘erectile tissue’: Two Corpora Cavernosa located dorsally and laterally on either side Ventrally in the middle is Corpus Spongiosum which encloses the penile urethra The Glans is made up of the enlarged tip of the Corpus spongiosum

Parts of the Penis:

Parts of the Penis

Root of the Penis:

Root of the Penis The root of the penis lies in the perineum and is not seen externally At the root of the penis you see two crura on either side which passes onto attach to the the pelvis by two ischiocavernosus muscles In the middle is the penile bulb through which urethra enters the penis it is covered by the bulbospongiosus muscle.

Pelvic Bones:

Pelvic Bones

Penis – Blood and Nerve supply:

Penis – Blood and Nerve supply Arterial blood is supplied by the branches of internal pudendal arteries. The veins drain into the internal pudendal and internal iliac veins Nerve supply is by both autonomic and somatic nerves Parasympathetic stimulation causes engorgement of the penis with blood and erection

Function of the Male Reproductive System:

Function of the Male Reproductive System The overall function of the male reproductive system is therefore to produce sperms and transmit them to the female reproductive system where they unite with the ova. In addition it carries out an endocrine function too. Different structures carry out different roles in carrying out this overall function

Endocrine function and regulation:

Endocrine function and regulation The testes produce the hormone testosterone. This is done in response to Luteinizing Hormone (LH) of the anterior pituitary which is a gonadotrophin The Follicular Stimulating Hormone or FSH, the other gonadotrophin secreted by the anterior pituitary stimulates the germ cell layer of the seminiferous tubules to produce sperm The release of LH and FSH is controlled by GnRH ( Gonadotrophin Releasing Hormone) from the Hypothalamus

Testosterone:

Testosterone Responsible for the development of and sustenance of masculine traits of the man, mainly occurs during and after puberty It also helps and is vital for the production of sperm in the seminiferous tubules in the testes. Testosterone affects the central nervous system and is responsible for the male aggressive behavior

Puberty in the Male:

Puberty in the Male It is a developmental stage during which secondary sexual characteristics appear and both males and females acquire the capacity to carry out sexual reproduction. It occurs between the ages of 10 to 14 years in the male LH from the anterior pituitary increase the secretion of testosterone from testes Testosterone induce the development of secondary sexual characteristics in the male

2ry sexual characteristics in the male:

2ry sexual characteristics in the male Increase in height, weight, muscle and bone mass of the body Enlargement of the larynx and deepening of the voice Growth of hair on the face, axillae , chest, abdomen and pubic area Enlargement of the penis, scrotum and prostate gland Maturation of the seminiferous tubules of the testes and production of spermatozoa. Though sexual ability and fertility declines with age, in the males there’s no period comparable to female menopause!

Spermatogenesis:

Spermatogenesis Is the process by which spermatozoa is produced in the seminiferous tubules of the testes (Meiotic Cell Division) It is arrested until puberty and only after the puberty or sexual maturation of the child into an adult, the process starts. It is stimulated by FSH and also supported by testosterone produced by the anterior pituitary and testes respectively

Spermatogenesis:

Spermatogenesis In the man a complete cycle of spermatogenesis - that is the first division of the germ cell to release of spermatazoa to the lumen of seminiferous tubules takes 64 days However in the testes there are germ cells of four different stages of maturation equally. These stages are equally spaced in time. This means there is a new batch of spermatozoa every 16 days in the testes.

Spermatogenesis:

Spermatogenesis However there is spermatozoa stored in the epididymis providing a good supply for ejaculations overcoming the need for continuous production. The spermatozoa released to the lumen of the seminfierous tubule are still immature. They become matured and motile only during their storage in the epididymis

Semen:

Semen Semen is the fluid that is ejaculated into the vagina by the penis during sexual intercourse Each ejaculate consists of 2 to 5 ml of fluid that contains 50 to 100 million sperm cells -the male germ cells The fluid of Semen provides nourishment and protection to sperm and comes from several sources: The fluid secreted by the seminal vesicles The secretions of the prostate gland The secretions of the glands of the mucus membrane of the urethral epithelium

Sperm :

Sperm

Sperm:

Sperm Sperm is the specialized germ cell of males with only 23 chromosomes It also has a specialized shape and structure and is motile in the semen Head contains the nucleus while a midsection has a series of mitochondria that provide energy for their motility. At the end is a tail that aids motility they are surrounded by a thin cytoplasm covered in plasma membrane. At the top of the head is a cap with enzymes that help the sperm to breakdown the ovarian membrane. Outside on dry surfaces sperm dies when the semen dries. However they may live in warm or wet conditions. Inside the female body it could live up to several days – up to about 5 days

Sperm:

Sperm Only one sperm is required to fertilize an egg. However there are about 100 million in each ejaculate of semen. This is because the sperm has to travel within the reproductive tract to meet the egg an only few sperm survive through this journey. Therefore there is an excess production. If the sperm count is less than 20 million/ml the person may be infertile. Similarly sperm motility or morphology too affects the health of sperms therefore fertility of a male.

Functions - Summary:

Functions - Summary Scrotum – Provides a site outside the body with a temperature less than body temperature that is conducive for production of semen Testes: Seminiferous tubules produce sperm by meiotic division stimulated by FSH of anterior pituitary and testosterone Interstitial cells ( Leydig cells) produce tetosterone stimulated by LH of anterior piuitary which maintains secondary sexual characteristics and male type aggressive behavior in males Epididymis stores newly produced spermatozoa where they acquire their final maturity and motility

Functions - Summary:

Functions - Summary Vas Deferens: transport the spermatozoa from the epididymis for ejaculatation during coitus Seminal Vesicles, Prostate Gland and Glands of the Urethra – provide fluid that nourishes and protect the spermatozoa. They provide the fluid component of the semen. Ejaculatory Ducts – transport the secretions of the seminal vesicles to the prostatic urethra to form semen together with sperm in the vas deferens. Semen – the fluid containing sperm ejaculated out of the penis into the female reproductive tract during intercourse.

Penis:

Penis Penis provide the final common pathway of the semen through urethra that runs through it. It is the organ with which sexual intercourse is accomplished and semen with sperm is deposited inside the female body during coitus To perform this task penis erects during coitus and also ejaculates semen out of urethra. Erection is accomplished by the erectile tissues in the penis

Erection & Ejaculation:

Erection & Ejaculation The erectile tissue have venous sinuses in them. During sex (arousal) the autonomic nervous system to the penis activates and the arteries are dilated increasing the blood supply. The extra blood engorges the sinuses of the erectile tissues of the penis The veins become compressed and drainage of blood is reduced further engorging the sinuses of erectile tissues The penis become elongated, stiffened and enlarged in order for it to penetrate the vagina. Smooth muscle contraction of the vas and the muscles around the penis cause the semen to ejaculate at the climax of sexual intercourse depositing sperm inside the vagina of female

End of Unit 12 – Part B:

End of Unit 12 – Part B

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