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Male Reproductive Tract - Horse Anatomy (view source)
Revision as of 13:52, 25 November 2022
, 13:52, 25 November 2022no edit summary
The parenchyma of the testes is composed of the '''semniferous tubules''', '''rete testis''' and '''efferent ducts'''. The '''semniferous tubules''' are the site of [[Spermatogenesis and Spermiation - Anatomy & Physiology|spermatogenesis]]. The walls of the semniferous tubules contain '''spermatogenic cells''' and their sustentacular cells, which are known as '''sertoli cells'''. The sertoli cells give support and also produce hormones. They regulate [[Spermatogenesis and Spermiation - Anatomy & Physiology|spermatogenesis]] and the release of spermatozoa into the lumen of the semniferous tubules. Each semniferous tubule opens into a network of tubules called the '''rete testis'''. Each rete testis is drained by multiple '''efferent ducts''' which perforate the capsule of the testes to enter the '''head of the epididymis'''. The interstitial tissue between semniferous tubules contains '''Leydig cells'''. These cells produce androgens, such as '''testosterone'''.
The parenchyma of the testes is composed of the '''semniferous tubules''', '''rete testis''' and '''efferent ducts'''. The '''semniferous tubules''' are the site of [[Spermatogenesis and Spermiation - Anatomy & Physiology|spermatogenesis]]. The walls of the semniferous tubules contain '''spermatogenic cells''' and their sustentacular cells, which are known as '''sertoli cells'''. The sertoli cells give support and also produce hormones. They regulate [[Spermatogenesis and Spermiation - Anatomy & Physiology|spermatogenesis]] and the release of spermatozoa into the lumen of the semniferous tubules. Each semniferous tubule opens into a network of tubules called the '''rete testis'''. Each rete testis is drained by multiple '''efferent ducts''' which perforate the capsule of the testes to enter the '''head of the epididymis'''. The interstitial tissue between semniferous tubules contains '''Leydig cells'''. These cells produce androgens, such as '''testosterone'''.
The Blood-Testes Barrier is formed by tight junctions between neighbouring Sertoli cells. This barrier prevents leukocytes from entering the adluminal compartment of the seminipherous tubules and autoreacting to the haploid spermatids within it.
The '''Blood-Testes Barrier''' is formed by tight junctions between neighbouring Sertoli cells. This barrier prevents leukocytes from entering the adluminal compartment of the seminipherous tubules and autoreacting to the haploid spermatids within it.
{{Template:Learning
|videos = [[Video: Equine Testes|Dissection of the equine testicle]]
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===Epididymis===
===Epididymis===
===Spermatic Cord===
===Spermatic Cord===
The spermatic cord comprises the '''ductus deferens''', testicular vessels and nerves. It runs from the abdomen caudally, through the '''inguinal canal'''. The inguinal canal is formed by the '''deep and superficial inguinal rings'''.
The spermatic cord comprises the '''ductus deferens''', testicular vessels and nerves, lymphatics and their serous coverings. It runs from the abdomen caudally, through the '''inguinal canal'''. The inguinal canal is formed by the '''deep and superficial inguinal rings'''.
*Deep inguinal ring: Opening between the ''internal abdominal oblique'', ''rectus abdominis'', prepubic tendon and inguinal ligament.
*Deep inguinal ring: Opening between the ''internal abdominal oblique'', ''rectus abdominis'', prepubic tendon and inguinal ligament.
*Superficial inguinal ring: Opening in the ''external abdominal oblique''.
*Superficial inguinal ring: Opening in the ''external abdominal oblique''.
===Lymphatic Drainage===
===Lymphatic Drainage===
The testicular lymphatics drain to the '''lumbar aortic lymph nodes''' and the '''medial iliac lymph nodes'''.
The testicular lymphatics drain to the '''lumbar aortic lymph nodes''' and the '''medial iliac lymph nodes'''. Lymphatics from the scrotum drain to the '''scrotal''' or '''superficial inguinal lymph nodes'''.
===Innervation===
===Innervation===
Nerve supply to scrotum and surrounding structures is provided by the '''ventral branches of the lumbar nerves''', '''iliohypogastric nerve''', '''ilioinguinal nerve''' and '''genitofemoral nerve'''.
Nerve supply to scrotum and surrounding structures is provided by the '''ventral branches of the lumbar nerves''', '''iliohypogastric nerve''', '''ilioinguinal nerve''' and '''genitofemoral nerve'''.
==Penis==
==Penis and Prepuce==
The penis is the male copulatory organ. It is formed from three parts; two Corpora cavernosa, comprising of cavernous tissue and a connective tissue sheath the tunica albuginea, and the single Corpus Spongiosum which contains the urethra encased in a vascular tissue sleeve. The penis can also be divided into the '''root''', '''body''' and '''glans'''. The horse has a musculovascular penis. In the '''musculovascular penis''', there is only a small amount of connective tissue, allowing them to be flaccid when not erect. Erection is accomplished by engorgement of the tissue with blood and a relatively larger ammount of blood is required to achieve erection than for a fibroelastic penis (ruminants, boar). Engorgement with blood increases the length and diameter of the penis.
===Root===
The root of the penis is the most proximal part, attached to the '''ischial arch'''. It consists of the '''crura''' and '''bulb'''. The '''crura''' consist of a '''cavernous tissue''' core surrounded by '''tunica albiguinea'''. The two crura converge to form the body of the penis. The '''bulb''' of the penis is an expansion of the '''corpus spongiosum''' around the pelvic urethra. The bulb lies between the two crura, close to the ischial arch.
===Body===
This is the main part of the penis, between the root and the glans.
====Corpus Cavernosum====
The corpus cavernosum is made up from the paired columns of erectile tissue (cavernous bodies) with enlarged venous spaces. Proximally, the right and left cavernous bodies separate, forming the two '''crura''' of the penis at its root.
====Corpus Spongiosum====
The corpus spongiosum is a vascular tissue sleeve surrounding the urethra. It commences at the '''bulb''' of the penis as an enlargement of the spongy tissue of the pelvic urethra. It is another column of erectile tissue, more delicate than the cavernous bodies. It contains larger blood spaces, divided by thinner septae. At the end of the penis the corpus spongiosum expands over the distal end of the corpus cavernosum to form the '''glans penis''', bringing the urethra to the extremity of the penis.
===Glans Penis===
The glans is the distal, free part of the penis. In the stallion, the glans penis is shaped like a mushroom, with the widest part being the '''corona'''. It then continues towards the body of the penis as the '''neck of the glans'''. The free end of the corona has a central fossa, the '''fossa glandis''', which receives the terminal urethra. The glans penis ends with the '''urethral process''', which is a protrusion of the terminal urethra.
===Prepuce===
The prepuce is the skin sheath that conceals the penis when it is flaccid and is formed by an invagination of the abdominal skin. The prepuce is hairless and contains many '''smegma''' secreting glands important for lubrication between the shaft of the penis and the prepuce during copulation. Within the prepuce are varying amounts of striated muscle fibres; the '''cranial prepucial muscles''' responsible for retracting the prepuce and the '''caudal prepucial muscles''' responsible for protracting the prepuce. Unlike other species, the prepuce of the stallion contains a second prepucial fold in order to accommodate the length of the penis in this species. The '''external fold of the prepuce''' corresponds with the prepuce of other species. The '''prepucial fold''' is a second fold inside the prepucial sheath, which ends at the '''prepucial ring''' cranially.
===Muscles of the Penis===
====Bulbospongiosus====
A single muscle that covers the root and ventral surface of the penis as well as the bulbourethral glands, extending to the apex of the penis. It is a continuation of the ''urethralis'' muscle. The function of this muscle is to empty the extrapelvic urethra of sperm in a similar way to the urethralis muscle emptying the pelvic urethra.
====Ischiocavernosus Muscles====
These are paired muscles located at the root of the penis which arise from the ischial arch and enclose the '''crura'''. They connect the penis to the ischial arch of the pelvis.
====Retractor Penis Muscles====
These paired muscles originate on the caudal vertebrae and insert on the ventrolateral surfaces of the penis. They follow the bulbospongiosus muscle to the apex of the penis.
===Vasculature===
The artery of the penis is a direct branch off the '''internal pudendal artery'''. It splits into three branches:
*Artery of the bulb – supplies the corpus spongiosus
*Deep artery of the penis – supplies the corpus cavernosum
*Dorsal artery of the penis – supplies the glans penis
The '''prepuce''' covering the flaccid penis is supplied by anastamosis between the '''external pudendal artery''' and the '''artery of the penis'''. In the stallion, there are additional anastamoses between the '''dorsal artery of the penis''' and the '''obturator artery'''.
===Innervation===
*Mostly parasympathetic from the paired '''pudendal nerves'''
*The glans penis and internal lamina of the prepuce are heavily infiltrated by sensory nerve endings, responsible for stimulating ejaculation
===Lymphatics===
Lymph from the penis and prepuce drains into the '''superficial inguinal lymph nodes'''.
{{Learning
|videos = [https://wikivet.mediacore.tv/media/equine-penis-potcast Equine penis potcast]
}}
==Accessory Sex Glands==
==Accessory Sex Glands==
Accessory sex glands are all found along the length of the pelvic urethra. They produce secretions containing lots of different components many of which can be found also the blood. One of the most important substances is fructose which provides an energy source for sperm. Along with providing nutrition for spermatozoa sex gland secretions facilitate movement of the sperm as well as providing a physiological buffer against the acidic environment of the female tract. Development and function of the accessory sex glands is androgen dependant.
===Bulbourethral Glands===
The paired bulbourethral glands are found near the ischial arch either side of, and dorsal to, the urethra. They are approximately the size of a cherry. These are very dense glands containing a lot of fibrous connective tissue.
===Prostate Gland===
The prostate is a singular gland, found at the junction between the bladder and the urethra. The stallion has only the compact part of the prostate ('''corpus prostate'''), which is a compact body of tissue found external to the urethra.
===Ampullary Glands===
These paired glands are found lying on the dorsal neck of the bladder. They develop due to a glandular enlargement within the wall of the ductus deferens as it crosses the dorsal surface of the bladder. The glands are connected to the urethra via the '''ejaculatory duct'''.
===Vesicular Glands===
The paired vesicular glands are found dorsocranial to the pelvic urethra. In the horse, the '''excretory duct''' from the vesicular glands join the ductus deferens to form the '''ejaculatory duct'''. They are also relatively large in the horse and are hollow with a thick, muscular wall and smooth surface.
==Clinical Links==
*[[Paraphimosis]] is the protrusion of the penis and inability to retract it.
*[[Castration Complications - Horse|Castration complications]]
[[Category:To Do - AP Review]]
==Webinars==
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