Male Reproductive System
The male reproductive system is responsible for:1-Production, nourishment & temporary storage of haploid male gamates (spermatozoa).
2- produce secretions that provide nutrients for spermatozoa . Spermatozoa and the secretions make up the semen
3-Production of male sex hormones (Androgens).
The male genital system consists of:Testis: produce spermatozoa &synthesize & release androgen.
Epididymis, Vas deferens, Ejaculatory duct & Part of male urethra : which form the ductal system which carries the spermatozoa to the exterior.Seminal vesicle, Prostate & Bulbourethral gland (of Cowpers) which are secretory glands provide fluid & nourishment to the spermatozoa & form the bulk of semen.
Penis
The testis, epididymis, & vas deferens are located in the scrotal sac which is a skin-covered pouch enclosing a mesothelium lined cavity continuous with peritoneal cavity of the inguinal ring.
Testis:
These are paired organs located outside the body cavity in the scrotum means that they are maintained in a temperature approximately 2-3 oc below the body temperature, this lower temperature is important for spermatogenesis, the testis developed in a high position on the posterior abdominal wall & migrate to the scrotum, usually arrived at the 7th month of the intrauterine life, when the testis fail to migrate to the scrotum a condition called (Cryptochidism), they fail to produce sperm.Each mature testis is a solid organ, ovoid, the right testis is larger & heavier than the left one.
Each testis has an epididymis attached to its posterior surface & it is suspended in the scrotal sac by the "spermatic cord" containing vas deferens, venous plexus & lymphatic vessels.
Scrotom:
It is covered by:
Skin: containing hair follicles & numerous eccrine sweat glands.
Deeper to the skin there is smooth muscle fibers arranged in a rather haphazard manner forming "Dartos muscle
Beneath Dartos muscle lies a fibrocollagenous fascia called "Colle's fascia".
Deepest layer of the Colle's fascia compacted to form a dense parietal layer of Tunica Vaginalis which is lined by flattened mesothelial cells; this layer forms the outer layer of the scrotal sac which is a potential space containing a watery fluid acts as a lubricant allowing testis to move freely without friction.
The testis covered by a thick collagenous capsule or called (the visceral layer of the tunica vaginalis) or called (tunica albuginea), it's outer surface is coated with flattened mesothelial cell layer, The tunica albuginea is thickened posteriorly to form the "mediastinum", fibrous septa from this mediastinum divide the body of testis into 250-350 lobules, and each lobule contains 1-4 seminiferous tubules.
Seminiferous Tubule (S.T):
It is a coiled non-branching closed loop both ends of which open into the "rete testis" which is a system of channels located at the posterior hilum of the testis close to the mediastinum.Each seminiferous tubule is approximately 80 cm long, each S.T has a central lumen lined by an actively replicating epithelium called "germinal epithelium" or "spermatogonia mixed with a population of supporting (sustentacular ) cells called the "Sertoli cells".. The S.T is surrounded by a well-defined basal lamina and a fibrous connective tissue consisting of several layers of fibroblasts .The innermost layer, adhering to the basal lamina, consists of flattened myoid cells which have characteristics of smooth muscle
Spermatogenesis:
Spermatogenesis is the process by which spermatozoids are formed. It begins with a primitive germ cell, the spermatogonium which is a relatively small cell, situated next to the basal lamina of the epithelium. At sexual maturity, spermatogonia begin dividing by mitosis, producing successive generations of cells. The newly formed cells can follow one of two paths: they can continue dividing as stem cells, also called type A spermatogonia, or they can differentiate during progressive mitotic cycles to become type B spermatogonia. Type B spermatogonia are progenitor cells that will differentiate into primary spermatocytes. The primary spermatocyte has 46 (44 + XY) chromosomes .Soon after their formation, these cells enter the prophase of the first meiotic division. Because this prophase takes about 22 days,. The primary spermatocytes are the largest cells of the spermatogenic lineage.
. The first meiotic division leading to the formation of diploid secondary spermatocytes which rapidly within few hours undergo the 2nd meiotic division to produce spermatids.
Spermiogenesis:-
Is the process by which haploid spermatids are transformed into spermatozoa, spermiogenesis can be divided into 4 stages all of which occur while the spermatids are embedded within small hollows in the free luminal surface of the sertoli cells, these stages are:
Golgi phase
Cap phase
Acrosome phase
Maturation phase
The mature spermatozoon is formed from (head, tail, the latter being composed of neck, middle piece, principle piece and end piece).
1-The head of mature spermatozoon is flattened and pointed composed of nucleus covered by acrosomal cap..The acrosomal cap cover the anterior 2/3 to 3/4 of the nucleus, it is a glycoprotein containing numerous enzymes including (protease, acid phosphatase,).The acrosomal cap enzymes are released when the spermatozoon contacts the ovum, they facilitate penetration of the corona radita and zona pellucida of the ovum by the spermatozoon nuclear head.
2-The tail region: is responsible for the spermatozoon motility, it is a long specialized cilium ( flagellum)with 9 outer douplets tubules around a central pair( 9٭2+2= 20)of tubule forming what is called axoneme runs throughout it’s length, the tail consists of :
Neck: a short narrow segment forming the proximal portion of the tail consists of a pair of centriole & connected to the remaining parts by a connecting piece
Middle piece: which consists of nine fibrous rings around the axoneme surrounded by outer zone of highly packed elongated mitochondria. , the lower limit of the middle piece is marked by a sudden narrowing (annulus).
Principle piece: Is the longest part of the tail & comprises the axoneme surrounded by the nine coarse longitudinal fibers which in turn enclosed by another circumferential external sheath fibers.
End piece: is composed of axoneme only because both the longitudinal & circumferential fibers disappear.