Week 1 Flashcards
1
Q
What is viviparous?
A
Live young
2
Q
What are the key aspects of reproduction?
A
* Production (an exocrine activity) and transport of ova
* Provision for deposition (copulatory organ) and transport of spermatozoa
* Provision of an environment for fertilization that nourishes and protects the conceptus
* Transport of conceptus and expulsion at parturition
* Endocrine activity (e.g. oestrogen and progesterone) which facilitates above activities
3
Q
What is an ovum?
A
The female reproductive cell or gamete of animals, which is capable of developing, usually only after fertilization into a new individual
4
Q
What are the four components of the reproductive system? Do they have the same embryonic origin?
A
- Germ cells
- Gonads
- Internal reproductive ducts
- External genitals
** each with separate embryonic origins
5
Q
What are the germ cells?
A
Arise outside the gonads and migrate into them; these are the progenitors of sperm and eggs
6
Q
What are gonads?
A
Testis and ovaries, arise on the medial surface of mesonephros (functions between the 6th and 10th weeks of embryological life– similar to the kidney– do not form the mature kidney); they promote germ cell proliferation and maturation and produce hormones/ growth factors that control development of other parts of the reproductive system
7
Q
What are the internal reproductive ducts?
A
Transport germ cells and in females support fetal development, have different origins in males and females
8
Q
What are the external genitals?
A
Incorporate parts of the urogenital sinus (endoderm- present in the development of the urinary and reproductive organs, it is the ventral part of the cloaca, formed after the cloaca separates from the anal canal during the fourth to seventh weeks of development), the proctodeum (ectodermal part of the alimentary canal– forms the lower part of the anal canal), and surrounding folds and the genital tubercle (develops into the glans penis or glans clitoridis)
9
Q
What does it mean to say the reproductive system is dimorphic? How does this occur (2 ways)?
A
Showing features that are substantially different in males and females.
Occurs by:
- forms a common progenitor then direct its differentiation towards male or female
- form separate male and female tissues, then only promote differentiation the appropriate set
10
Q
What are are primordial germ cells (PGCs)?
A
Progenitors of sperm and eggs. In all vertebrates they originate outside of gonadal tissues and secondarily move into the embryonic gonads.
** After the differentiation of testes or ovaries is underway, the germ cells (aka gonocytes) begin to proliferate rapidly. In human females, several million oogonia are generated before birth, but less than 2% survive until puberty, when hormonal stimulation initiates maturation of one or more latent oocytes during each estrus (menstrual) cycle
11
Q
What are teratomas?
A
Some PGCs do not reach the gonadal ridges, most of these die, but a few may survive in ectopic locations and can later form tumors called teratomas. Teratomas contain irregularly arranged masses of many tissues including hair, teeth, cartilage, and bone, cardiac and skeletal muscle, thyroid, pancreas, gut, and kidney. These represent derivatives of all embryonic germ layers.
** usually benign, cystic tumors, although cells within the teratoma may become malignant. Most teratomas arise in or near the gonads, but occasionally are found at the base of the spinal cord, in the neck, mediastinum (mesenteries of heart and lungs), lungs, pericardium, and brain.
12
Q
What is the path of differentiation of gonads into testes??
A
* Sex specific differentiation within the indifferent gonad is initiated earlier in males than in females
** First morphological changes are thickening of the basement membrane beneath the coelomic epithelium (tunica albuginea) and invasion of endothelial cells from the mesonephros
** Distal parts of many mesonephric tubules fuse with invaginated coelomic epithelial cords to form GONADAL CORDS, which become infiltrated by PGCs
** Later these cords cavitate to form SEMINIFEROUS TUBULES, where SPERMATOGENESIS will take place
**The mesonephric tubules remain and form the efferent ducts and rete testes which transport sperm to the epididymis (duct behind the testis, which sperm passes to the vas deferens), which is the region of the mesonephric duct that remains closely associated with the testis
** After testicular differentiation is underway, the caudal part of the mesonephros begins to degenerate, similar to the fate that already befell the cranial part of this organ
**
13
Q
A
14
Q
What are the Sertoli cells?
A
The first testis-unique cells to differentiate, derived from coelomic epithelium. These are critical for spermatogenesis following sexual maturation. In the embryo, these cells secrete AMH (anti-Mullerian hormone). This is a peptide hormone that initiates degeneration of progenitors of female reproductive ducts.
15
Q
What is anti-Mullerian hormone (AMH)?
A
This is a peptide hormone that initiates degeneration of progenitors of female reproductive ducts.
16
Q
What are Interstitial (Leydig) cells?
A
Some of the mesenchymal cells that surround the gonadal cords in the testis differentiate as interstitial (Leydig) cells. These cells synthesize and release testosterone, which is necessary to promote the subsequent differentiation and growth of mesonephric tubules and ducts. Testerosterone also promotes masculinization of the external genitals.
17
Q
What does testosterone do during development?
A
promote the subsequent differentiation and growth of mesonephric tubules and ducts. Testerosterone also promotes masculinization of the external genitals.
18
Q
What is the SRY gene?
A
Transcriptional regulatory gene that contains a region that codes for a DNA binding region of the peptide called HMG (high mobility group) – SRY binds to DNA and induces a conformational change, in effect creating a bend in the DNA. ** SRY marks the first gender specific event in gonadogenesis– activates Sox9 (autosomal gene)– expressed on both male and female gonadal ridges– sox9, the testis determining factor, binds to an AMH promoter, therefore leading to the regression of the paramesonephric (muellerian) ducts
** the SRY gene makes males– or without it, = female
One gene located on the Y chromosome (from a male) is required for male development. The gene activates other “boy” genes– without it, other “girl” genes are activated.
19
Q
What are the paramesonephric (muellerian) ducts?
A
Paired ducts of the embryo that run down the lateral sides of the urogenital ridge and terminate on the sinus tubercle in the urogenital sinus. IN the female, they will develop into the uterine tubes, uterus, and cervix and the upper one third of the vagina. IN the male, they are lost. Mesodermal origin.
20
Q
What are ovarian follicles? When can they become clinically relevant?
A
In females, the invaginating cords of coelomic epithelium (serosa) break apart into vesicular spheres called ovarian follivles, each of which initially contain multiple germ cells. Most of these are located around the margin of the indifferent gonad. All of the mesonephric tubules degenerate, as a result, the follicles fill the entire ovary. The mesonephric ducts largely degenerate in females, though nonfunctional remnants are occasionally found near the ovary and the urogenital sinus. These can be of clinical consequence if they become cystic.
21
Q
What is Wnt4?
A
Signaling factors critical to cell determination and differentiation in many systems, it was the first signaling molecule after AMH to be identified in early gonadogensis. Wnt4 has a suppressive effect on the differentiation of stroid producing cells, including interstitial (Leydig) cells, and Wnt4 mutations that specifically block this function result in females with excess steroid hormone production in their gonads, including low levels of testosterone.
** overexpression of Wnt4 produces a range of abnormalities in XY individuals. these range from mild e.g. cryptorchidism, to full feminization of teh reproductive ducts and external genitals.
22
Q
What is cryptorchidism?
A
The absence of one or both testes from the scrotum.
23
Q
A
24
Q
What gender are the mesonephric ducts retained and what do they develop into?
A
* In males, mesonephric ducts are retained. Within the mesonephros, where efferent ducts derived from mesonephric tubules are present, the duct becomes the epididymis. Caudally the mesonephric duct differentiates into the deferent duct (ductus deferens), which carries sperm from the epididymus to the urethra
* Near its junction with the urogenital sinus, a diverticulum from each mesonephric duct forms the seminal vesicle.
25
What is the ductus deferens (deferent duct)?
which carries sperm from the epididymus to the urethra
26
Where do the prostate gland and the bulbourethral glands arise from?
Arise as multiple small diverticula from the roof of the urogenital sinus immediately caudal to the mesonephric duct. This region becomes part of the pelvic urethra. All male mammals have a prostate gland, but some can be reduced or absent e.g. cat, dog.
27
28
Where do the female reproductive ducts differentiate from?
NOT associated with the mesonephric system. The "plumbing" components of the female reproductive system develop in both male and female embryos.
\* A longitudinal band of thickened serosa forms along the ventro-lateral margin of each mesonephros. Cells in each band invaginate, forming a pair of long goorves that close to form the paramesonephric ducts--\> the thickening, invagination, and closure extend caudally along the dorsolateral margin of the coelum--\> as the ducts elongate caudally-- they merge to fuse with the urogenital sinus
29
30
What prevents oocytes to be released from the surface of the ovary from escaping into other parts of the peritoneal cavity?
The arrangement of serosal folds functionally prevents oocytes released from the surface of the ovary from escaping into other parts of the peritoneal cavity, and directs them into the lumen of the duct.
31
What is different about the paramesonephric ducts between humans and other mammals?
\* in humans the paramesonephric ducts differentiate as the uterine tubes (formerly called oviducts)-- and the region where they are joined is the uterus, which is the site of the placental contacts during pregnancy.
\* in most mammals, embryonic development is supported along a much greater length of paramesonephric ducts; these are referred to as uterine horns. the uterine tubes remain as short segments close to the ovary and are the sites where fertilization occurs. The body of the uterus is often relatively small.
32
33
What forms the vagina in development?
The roof of the urogenital sinus evaginates at the site where the paramesonephric ducts enter. This evagination together with the distal part of the paramesonephric ducts forms the vagina, which is of both endodermal (urogenital sinus) and mesodermal (paramesonephric ducts) origin.
34
What is the vestibule?
In non-primate mammals, the vestibule is the chamber located between the sites of urethral and vaginal entrance and the body wall. It is largely of urogenital sinus origin, but its caudal region includes contributions from the surface ectoderm.
35
What is the genital tubercle?
Mesoderm ventrally adjacent to the UGS proliferates to form a swelling, the genital tubercle. This is present in both male and female embryos. After the onset of sex- specific gonadal secretions, both the growth and location of the genital tubercle change in male embryos. It will eventually go on to form the external genitals
36
What do the cloacal folds become?
Extending dorsally from the base of the genital tubercle on either side of the cloacal plate are cloacal folds (genital folds). These ridges extend laterally as genital swellings (labioscrotal swellings). After separation of the rectum from the urogenital sinus, the cloacal folds become anal and urethral folds.
37
What do urethral folds become?
In females, urethral folds and genital swellings enlarge to form the labia. Ventrally they partially circumscribe the genital tubercle, which will form the clitoris.
\*\* In males, the urethral folds meet in the midline and fuse, initiating the closure of the penile urethra. This apparent increase in the distance from the anus to the base of the penis (anogenital distance) is the earliest external sign of male development. The genital swellings remain as the scrotum.
38
What converts testosterone to DHT? What is DHT?
The enzyme 5-alpha-reductase type I converts testosertone to dihydrotestosterone (DHT) which is the essential activator for growth and differentiation of precursors of the penis and scrotum.
39
What happens when there is a dysfunction of 5-alpha-reductase-1?
Renders the external genitals nonresponsive to testosterone, a condition referred to as testicular feminization. Complete loss of this reductase in XY fetuses produces an infant tha tmay appear female at birth, but will later not menstruate and at puberty will develop male secondary sex features.
40
What is a male's phenotype? Female?
XY, female= XX
41
What is an example of a common progenitor being directed to differentiate along either of two pathways?
Gonad
42
What is the 47XXY genotype (Klinefelter syndrome)?
\*\* Intersex condition
A result of meiotic X-chromosome nondisjunction during oogenesis. These persons are phenotypically male. They have male internal reproductive tracts (i.e. mesonephric ducts), lack oviducts, and uterus, and have male external genitals. Small testes (primary hypogonadism) and lack mature sperm. Due to reduced levels of post-puberty circulating testosterone, they develop secondary signs such as increased fat accumulaton on the hips and unusually long extremities.
\*\* Many calico (tortoiseshell) cats affected and 3 color males (orange and not orange- need two X chromosomes)
43
What is the XO genotype in females (aka Turner syndrome)?
Occurs less frequently than XXY individuals.
\*\* intersex condition
\* Affected persons are phenotypically female, sterile, and usually present with short stature, lateral webbing of the neck and cardiac malformations.
\*\* Horses-- female but may be small for age and breed. Ovaries are small and inactive and the individual is sterile
44
What is "intersex conditions" (pseudohermaphroditism)?
Secondary sex characteristics of an individual do not match the gonads (ovary or testis).
\* external reproductive organs may look like typical penis or clitoris or in some cases may look "intermediate"
45
What is a true hermaphrodite?
\* Both ovarian and testicular tissue is present
46
What is a Freemartin?
\* More than 90% of heifers who are born as twin to a bull calf, are sterile. These animals become XX/XY chimeras due to placental anastamoses, in which blood (cells) cross from one twin to the other. The external genitals often show some masculinization, such as enlarged clitoris or increased ano-genital distance. Typically, the internal reproductive ducts are ambiguous.
\*\* picture: the one on the right is normal-- the abnormal- vagina is short- without ultrasound, you can just measure
47
What do the uterine tubes do? (fallopian or oviduct)
Funnel shaped entrance (infundibulum)-- located at the ovarian end, leading into the uterus at the other. The uterine tubes collect and conduct the ova to the uterus and are generally the site of ferilization of the oocyte.
48
What is the uterus?
A single structure but comprising 2 horns (which are the most developed region in the domestic animals), a body (relatively short, single tube), and a cervix (thick walled caudal portion of the uterus akin to a valve-- closed except during oestrus or parturition. The uterus receives the zygote and provides an environment for implantation and development of the conceptus.
49
What is the vagina and vestibule?
The contiguous distal portions of the tubular genitalia serving as the copulatory organ and birth canal. The junction between the vagina/ vestibule is marked by the external urethral orifice.
50
What is the vulva?
The external opening of the tract and comprises a median cleft that is flanked by a labium either side, which meet dorsally and ventrally at the dorsal and ventral commissures.
51
What are the major areas of variation seen among the domestic animals?
\* ovarian size, shape, internal organization and location, uterine shape, relative sizes of the uterine horns and uterine body, internal morphology and location, cervical length and the tortuosity of the cervical canal.
\* Birds-- usually a single ovary (usually left) that appears lik ea bunch of grapes-surface covered with very large oocytes
52
What is the oestrus cycle?
Comprises alternating periods of receptivity for mating and periods of indifference. The lengths of thse periods are their frequency are species dependant
53
What is oestrus?
The period of receptivity and generally coincides with ovulation (release of the oocyte). Around oestrus the follicles in the ovary grow to maturity and rupture, the cervix opens and the vagina/ bulva prepares for copulation. The trace prepares for transport of spermatozoa and fertilization of the ova.
54
What the corpora lutea?
\*\* following oestrus the corpora lutea form from the ruptured follicles and the uterine vasculature increases and the uterine mucosa prepares to support the conceptus. If fertilization fails the corpora lutea degenerate and a new set of follicles begin to mature and the uterus begins to return towards its resting state
\*\* if fertilization is successful the corpus lutea in the ovary are retained and the uterine changes (mucosal and vascular) are more marked with the formation of the placenta to nourish the conceptus during gestation
55
56
Location of ovaries in ruminants and pigs vs. other species
Ruminants and pigs-- ovaries are located close to or at the pelvic inlet having undergone a caudal migration somewhat akin to "descent" as applied to the male gonads which descend into the scrotum.
\*\* coil shaped in ruminants and convoluted in the sow
\*\* other species- sublumbar region caudal to the kidneys- near where they arise embryologically
57
What is unique about the equine ovary?
The cortical tissue (stroma, follicles, and corpora lutea) are located in the centre of the organ, while the medullary tissue occupies the outer region. The cortical tissue comes to the surface at the depths of a small depression (ovulation fossa) on one side of the ovary.
58
What is the mesovarium?
medulla consists of loose connective tissue containing vessels and nerves and contacts the surface at the hilus- Where vessels and nerves enter and where the ovary attaches to its mesentery (mesovarium)
\*\* ovarian a. runs in the mesovarium
59
What is the cortex of the ovary made up of?
Dense stromal tissue of plump fibroblast-like cells and connective tissue. Scattered within the cortex are spherical structures- follicles and corpora lutea.
60
What are ovarian follicles? What are corpora lutea?
Fluid filled spheres which contain oocytes, and are in various stages of development. The corpora lutea are also spherical bodies but consist of endocrine cells which produce progesterone to support pregnancy.
\*\* Follicles and corpora lutea go through cyclic changes of development, rupture and regression. Thus the composition and appearance of the cortex varies associated with the stage of the oestrus cycle in the mature animal. It will contain follicles (each containing an ovum) at various stages of developemtn and varying in size from microscopic primordial follicles to macroscopic mature tertiary follicles...
61
What is the major factor influencing siz of the follicles?
The amount of follicular fluid present.
62
What is atresia?
Follicles undergoing degeneration
63
What develops from follicles following ovulation?
Corpora lutea-- generally attain a similar size to that of the mature follicle of a given species.
\*\* they undergo degeneration (if no pregnancy or after parturition) to form scars called corpora albicantes-- which gradually shrink over successive cycles and eventually disappear
64
What gives the ovaries the irregular, nodular appearance?
Follicles and corpora lutea generally protrude from the ovarian surface-- the degree depends on species
65
What do follicles produce? What do corpora lutea produce?
Oestrogen and cause signs of oestrus or heat and promote conditions favouring fertilization and support of the ovum and zygote.
\* Corpora lutea produce progesterone which supports pregnancy
66
What is the tunica albuginea?
Surrounding the cortex is a thin layer of dense connective tissue- tunica albuginea. This underlies the ovarian surface epithelium which is a simple epithelium of variable height. This epithelium is continuous with the ovarian mesentery.
67
68
What does the infundibulum at the ovarian end of the uterine tube do?
Leads to the abdominal opening of the tube- the ostium- located at its base. The free margin of the infundibulum is irregular and forms processes called fimbriae which extend towards the ovary.
\*\* the infundibulum and fimbriae become active and motile at ovulation and move close to the ovary to catch and sweep the ova towards and through the ostium into the uterine tube
69
What does the ostium lead to?
Relatively wide lumen of teh initial segment called the ampulla, this is followed by the isthmus which has a narrower lumen but equal length. The isthmus ends at the uterotubal junction with the uterine opening which may be located on a small papilla which projects into the uterine lumen or the transition may be gradual depending on species.
70
What does the uterus consist of?
Uterus, body, cervix
\*\* largest portion of the reproductive tract and provides for the protection and nourishment of the embryo/foetus until parturition, and assists in the expulsion of the foetus at term
71
What is different about uterine horns in a pig vs. ruminant?
Luminal surface may possess varying order of folds in pigs
Or
rows of small mounds (caruncles) in ruminants
72
What is the cervix?
Thick walled terminal portion of the uterus and is located between the uterine body cranially and the vagina caudally.
Wall comprises smooth muscle and dense fibrous tissue which makes it easily distinguished by palpation in the large domestic animals. It acts as a sphincter or valve regulating access to the uterus from the vagina.
\*\* a seal is completed with a plug of cervical mucous
73
What is the vagina?
Thin walled, highly distensible tube extending from the cervix to the vestibule. Usually in a collapsed state. Only a small cranial portion of the dorsal aspect is covered by peritoneum, the site offer surgical access to the abdominal cavity (via the rectogenital pouch).
\*\* forms the cranial portion of the copulating organ of the female birth canal. It receives the penis of the male during copulation and is the site of seminal fluid deposition in ruminants.
74
What is the hymen?
\* found near the caudal end of the vagina and marks the boundary between structures of different embryological orgins. It is poorly developed in the domestic animals ranging from a low annular fold to a series of short transverse folds or irregular tags.
75
What is the vaginal fornix?
The annular recess at the cranial end of the vagina-- formed around the vaginal portion of the cervix.
76
What is the border between the vagina and vestibule called?
External urethral orifice
77
WHat is the vestibule?
The vestibule is
the short terminal portion of the tubular genitalia that is shared with the urinary
system.
It is the caudal part of the copulatory organ and birth canal and extends from the vagina to the
vulva. It lies caudal to the ischiatic arch and is generally incli
ned ventrally.
78
What anatomical features make catheterisation of the urethra in a female difficult?
\* the external urethral orifice is raised above the tract floor on a small mound or HUMMOCK in the bitch (where the urethra enters), while the cow and sow there is a small pocket called the suburethral diverticulum.
79
WHat are the vestibular glands?
The wall of the vestibule has mucous glands-- major and minor. Provide lubrication for the tract in preparation for copulation and parturition. Mucus production is most pronounced during oestrus.
\* minor vestibular glands- several rows of simple galnds opening on the lateral +/- ventral wall of the vestibule in the dog, pig, and horse, and are variably present in sheep
80
What is the vestibular bulb?
\* the wall of the vestibule contains extensive venous plexuses. IN the bitch and mare these form discrete patches on either side. This cavernous or erectile tissue is homologous to the penile bulb in the male.
81
What is the clitoris?
Comprises of 2 crura, a body and a glans and is homologous to the male penis. It contains erectile tissue in the mare and bitch.
\*\* the glans in the mare has multiple sinuses which can serve as hideouts for venereal pathogens (clitoralfossalectomy to prevent- probably uncommon)
\*\* Mare has more erectile tissue in the clitoris (winking)
\*\* older mares it can start to slope dorsally and get faecal contamination
82
What is the constrictor vestibuli m.
Vestibule is encircled by circular skeletal muscle.
83
What is the vulva?
External opening of the female repro tract. Comprises of a vertical cleft flanked laterally by 2 labia. The labia meet dorsally at the dorsal commissure and ventrally at the ventral commissure. (the ventral commissure encloses the clitoris).
84
Describe the labia
\*\* the skin of the labia is common integument with many sebaceous and sweat glands with fine hair
\*\* the labia contain fat and muscle bundles, the latter being the constrictor vulvae m.
85
What ligament suspends the female repro tract from the roof of the abdomen? What 3 parts is it made up of?
Broad ligament
1. mesovarium
2. meosalpinx
3. mesometrium
86
What is the mesovarium? What are the other two ligaments associated?
The most cranial part of the broad ligament and supports the ovary. It attaches to the hilus and carries vessels and nerves to the ovary.
\*\* cranial free border is thickened to form the suspensory ligament of the ovary
\*\* proper ligament- runs between the uterine pole of the ovary to the cranial tip of the ipsilateral uterine horn
87
What is the mesosalpinx?
\* supports and encloses the uterine tube-- a fold of peritoneum arising from the lateral surface of the mesovarium -- which forms a small pouch, the ovarian bursa (which contains the ovary in carnivores, but is too small to do so in the mare)
88
What is the mesometrium?
\* supends the uterine horns, body and cervix and is continuous with the perimetrium of the uterus (outer serosal covering). It carries the vessels and nerves serving the uterus.
\*\* the lateral surface of the mesometrium on either side has an additional fold of peritoneum which runs to the inguinal canal. Each one's cranial free border carries a round ligament of the uterus (a vestigial structure) which continues through the inguinal canal into the vaginal process. Varies in developement depending on species (may be seen in carnivores, hores and cow)
\*\* uterine a. runs in the mesometrium
89
What is the arterial arcade? What arteries contribute?
The blood vessels supplying the reproductive tract form numerous anastomoses which form an arterial arcade running the length of the uterus. This arcade receives contributions from the following arteries: ovarian a., uterine a., and vaginal a.
90
Where does the ovarian a. arise from? What does it branch to?
Arises from the aorta--\> runs within the mesovarium--\> gives rise to an ovarian branch, a uterine branch and a branch to the uterine tube
91
Who has the uterine a.? Where does it run? What does it give rise to?
Uterine a. runs within the mesometrium and gives rise to branches that run cranially and caudally. The vessel arises from the internal iliac a. via the umbilical a. in the ruminant and pig and from the external iliac a. in the horse. It is absent in carnivores. When present, it is the major supply to the uterus.
92
What is fremitus?
In large ruminants and the pig, palpable turbulence can be felt in these vessels at certain stages of pregnancy (cow 80-90 days + in artery of the gravid horn)
93
Which is the most caudal of the main blood vessels supplying the repro tract? Where does it arise from in diff. species?
\* vaginal a. is th emost caudal-- gives rise to branches running cranially and caudally
\* internal pudenal a in the horse
\* internal iliac a. in the ruminants and pig
94
What is usually the largest vein? What is the plexiform structure?
\* Ovarian v.
\* Plexiform strcutre is usually near the ovarian a.-- adopts a tortuous course, similar to the testicular vessels in the male-- this arrangement is involved in endocrine signalling to the ovary from the uterus and is particularly well developed in the pig and ruminants.
95
What do PGCs become, what is the end state? Talk through the development
PGCs become oogonia. Oogonia within follicles enter meiosis to become primary oocytes--\> thus establishing primordial follicles
96
What hormones from the anterior pituitary influence the follicle?
Gonadotrophins, follicle stimulating hormone (FSH), luteinizing hormone (LH)
97
What facilitates production of androgens? WHat does this eventually produce?
Luteinizing hormone.... eventually producing oestrogens
98
WHat is oestrogen under the influence of? What do they do?
FSH
Create a favourable local environment, act on the reproductive tract, and cause the typical and classical behavioural signs of oestrus
99
What is there a surge in at to initiate ovulation?
LH
100
What does ovulation involve?
The destruction of the follicular wall and release of the oocyte, which is then swept into the uterine tube. This is brought about with an increase in the secretion of follicular fluid, further protrusion of the follicle from the ovarian surface, thinning of the follicular wall over the point of rupture, due to the activity of collagenase and the initiation of an inflammatory response, and the degradation of the ground substance holding the oocyte within the cumulus oophorus. At this time the oocyte may complete the 1st meiotic division depending on species.
101
Wolffian duct- mesonephric system
102
Tubular genitalia- a system of connected muscular tubes
103
Infundibulum is a mitt of the uterine tube. Catches the ovum (baseball)
\*\* ovum is fertilized in the uterine tube
104
What is this picture? What is unique about the horse's ____ (#4)?
Ovary (with the hilus- nerves and blood vessels)
When the follicles (bumps) rupture- they form the corpus luteum.
\*\* Horses are inside out
105
What is extremely important for spermatogenesis?
Temperature!
In humans- 2 C cooler than body temperature, in rodents 8 C cooler
\*\* Blood cools down as it goes down the testicle
106
What is in the testis?
\* Seminiferous tubules- myofibroblast cells-- having to do with squeezing the sperm when it is mature into the epididymis-- on the outside at the lumen of the seminiferous tubules are the germ cells (spermatogonia)-- after maturity they tend to undergo mitosis and meiosis. In the lumen of the tubule-- spermatazoa
\* Sertoli cells - supportive cells for the sperm
107
What is in the seminiferous tubules?
108
What do Sertoli cells do?
\* Create tight junctions to protect testis (BLOOD TESTIS BARRIER-- to reduce chance of autoimmune disease and other disease)
\* supportive cells for sperm
\* Separate apical and basal compartments
\* produce hormones, small amounts of oestrogen too.
109
110
What happens in spermatogenesis
1. Spermatocytogenesis- spermatogonia give rise to spermatocytes
2. Meiosis- diploid cell to a haploid cell- important for a gamete. Spermatocytes gives rise to spermatids
3. Spermiogenesis- spermatids transform into spermatozoa (familiar tail things)
111
What is interesting about the cells when creating spermatozoa?
They are joined until they are spermatocytes
112
What is responsible for producing androgens (testosterone)?
Testis
Interstitial (Leydig) Cells in testicles- make testosterone- not affected by temperature-- site between seminiferous tubules
113
How is sperm conducted to the urethra?
Testis--\> epididymis--\> ductus deferens (ampulla at the top-- V shaped)-- in some animals widens out to become ampulla... which often secretes chemicals that assist in seminal fluid... ampulla can sometimes be considered an accessory gland in SOME species: ruminants, horses, and dogs (remember by thinking they all PULL THINGS)
\*\* the last part is the ejaculatory duct in horses and ruminants
114
What is the role of the epididymis?
\* site of where sperm mature
\* also conduct sperm
115
What is the seminole colliculus (colliculus seminalis)?
Where the ampulla joins into the urethra
116
What kind of tissue does the urethra have?
\* urethra has erectile and cavernous tissue
117
What is seminal plasma (semen)? What produces semen?
Semen is the fluid that nourishes sperm.
Accessory glands produce semen (a few different ones)
118
What are seminal vesicles?
\* adds parts to semen
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What are bulbourethral glands? What are the other glands that have to do with semen?
Cylindrical structures in bulls- add parts to semen.
\*\* prostrate gland also adds to the seminal plasma-- colourless, slightly acid fluid, high concentration of proteolytic enzymes, zinc and copper (especially dog)
\*\* seminal vesicles- mesonephric duct origin-- slightly yellowish secretion, presence of flavines, potassium and fructose concentrations. Ergothionine (in the boar especially) citric acid, proteins, prostaglandins are also present
120
What happens to retractor penis muscle?
Has to relax during erection.
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Barbs on the penis cause cats to ovulate
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What is the role of the ischiocavernosus m.?
Pumps blood into the corpus cavernosum
Positions penis during intromission and coitus
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What is the role of the bulbospongiosus m. ?
Pulses during ejaculation to assist in expulsion of semen
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What is the role of the retractor penis mm.?
Retraction of the penis into prepuse collowing coitus
125
What is the role of prepuce?
Covers the penis- protective structure
126
What is the colliculus seminalis?
Ridge of tissue-- multiple ducts open in the region of the colliculus seminalis of the urethra mucosa
127
Fibroelastic (with sigmoid flexure) vs. musculocavernous
Variation in structure of the corpus cavernosum penis is responsible for the classification of penises into 2 main types:
1. the fibroelastic or fibrous type (with very little erectile tissue- the bulk of the structure being fibrous and elastic connective tissue-- S shape bend when quiescent-- PRESENT IN RUMINANTS AND PIGS)
2. the musculocavernous or muscular type- relatively little erectile tissue- tunica albuginea and septa being less substantial than above, much smooth muscle present. HORSES AND CARNIVORES (in carnivores, the corpus cavernosum is ossified and forms the os penis)
128
What are the background influences on male reproduction to be considered?
129
What are some of the areas of the brain and some of their functions needed by the male?
Optic chiasm, pituitary gland, hypothalamus, sella turcica (bone)
130
What is a sexually stimulating environment?
\* Others mounting (sense of sight)
\* Sexual arousal
\* pheromones (sense of smell)
\* Bull touches/ rubs/ licks cow (sense of touch)
\* Cow stands still
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What evokes libido?
\* Male sexual behaviour patterns imprinted on the brain in foetal/ neonatal life
\* Testosterone in the adult evokes the imprinted pattern
\* Testosterone threshold
\* previous experience, training
\*Management
\* Sexual stimulation/ environment prior to mating
\* Pain often adversely affects ability to serve
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Flehmen- a sign of sexual arousal
136
What are some causes of fluctuation in fertility?
137
What are factors affecting reproductive efficiency?
\* age (puberty, sexual maturity- plateau, old age- decline in efficiency)
\* breed (genetic constitution has a strong influence on sexual behaviour and testicular size)
\* season- reproductive efficiency absent or reduced during the non-breeding season in horses, sheep goats
\* Climate (especially un-adapted animals in tropical countries)
\* nutrition (poorly fed animals less efficient, increased dietary protein increases ram sperm production, obesity may inhibit libido and testicular function)
\* management (where and when males grouped with females, male: female ratio, dominant vs. subordinate males, fighting between males)
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Function of the horse pineal gland
139
What is the hypothalamic-pituitary-gonadal axis?
140
What is the anterior pituitary's role in reproduction?
141
Melatonin's role in reproduction?
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What axis produces melatonin? What is another chemical involved?
143
Sequence of events in the hormonal control of spermatogenesis in the bull
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Spermatogenesis
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What drives puberty? How old in bulls? Rams? Stallions? tomcats? dogs?
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Where does oestrogen come from?
Ovary.
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Oestrogen vs. oestrodial
Oestrogen- umbrella term
Oestrodiol- a type of oestrogen
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The most important reproductive hormones in the female.... What comes from the hypothalamus? Pituitary? Ovary? Uterus? Placenta?
\* Hypothalamus: GnRH
\* Pituitary: anterior lobe: LH, FSH, Prolactin
posterior lobe: oxytocin
\* Ovary: oestrogen, progesterone, inhibin, oxytocin, relaxin, some testosterone
\* Uterus: prostaglandin F2alpha
\* Placenta: progestagens, Oestrogens, (equine and human chorionic Gonadotropins only in horses and women respectively)
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Function of reproductive hormones?
\* release of other hormones
\* stimulation of the ovary (gonadotrophins)
\* sexual promoters (steroids)
\* Pregnancy maintenance
\* Luteolysis (destruction of the Corpus luteum)
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How is the male hypothalamus "defeminized?" Why is the female hypothalamus not "defeminized" like the male?
The hypothalamus is inherently female. The GnRH surge centre in the male is "eliminated" by testosterone during embryogenesis.
\*\* the male brain is "defiminized" by testosterone that is converted into oestradiol.
\* Femal fetal ovaries produce oestradiol, but it cannot cross the BBB because it is bound by alpha-fetoprotein and therefore cannot affect the hypothalamus
\* in the male, testosterone is crossing the BBB without any problem and is then converted into oestradiol in the brain
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What does onset of female puberty depend on?
1. Development of threshold body size (to carry a calf full term and deliver, for example)
2. Exposure to certain environmental or social cues
\*\* onset of puberty relies on the secretion of GnRH at the appropriate frequency and in sufficient quantities to stimulate gonadotropin release by the anterior pituitary.
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What is puberty? in the female? male?
The ability to accomplish reproductive success
In the female defined as:
- age at first oestrus
- age at first ovulation
- age at which female can support pregnancy without deleterious effect
In the male:
- age when behavioral traits are expressed
- age at first ejaculation
- age when spermatozoa first appear in ejaculate
- age when ejaculate contains threshold number of spermatozoa
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Which hormone triggers high surges of GnRH? WHat is the follow on effect?
Due to high levels of oestrodiol--\>GnRH--\> leads to LH/ FSH production
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What happens before puberty in both males and females in regards to GnRH?
GnRH neurons in the regions of teh tonic center and in the surge center of the hypothalamus release low amplitude low frequency pulses of GnRH
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What does the paraventricular nucleus do?
Neurons of the PVN produce oxytocin
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What is the average age (range) of puberty in different species? What plays a role intraspecies?
Breed
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What are the parts of the hypothalamus that influence reproduction?
nerve cells bodies that form the surge centre, tonic centre, and the paraventricular nucleus
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What does the surge and tonic centers of the hypothalamus produce?
Gonadotropin releasing hormone (GnRH)
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What is the communication between the hypothalamus and the anterior pituitary? How is the posterior pituitary different?
Hypothalamo-hypophyseal portal system
\* the posterior pituitary is different because it is not connected via the portal system and the hormones (such as oxytocin) are deposited directly through capillaries.
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What is a gamete?
A mature haploid (half the usual number of chromosomes) male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote (e.g. sperm)
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What makes a male and a female?
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What is TDF?
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What is Androgen Insensitivity Syndrome?
Partial or complete inability of cells to respond to androgens
\* complete AIS: XY individual looks like a female
\* partial AIS: genitalia partially masculinized
\* mild AIS: genitalia masculinized
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Cervix- designed to close and keep out any pathogens
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8? 10?
8- cervix
10- vagina
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Cervix-- tight and closed-- probably pregnant in diestrus. (This is a endoscopic view of the external uterine orifice)
IF it is floppy and open-- in oestrus
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What is a synonym for the vestibule?
Greeting room
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VX?
Vaginal fornix- annular recess around vaginal portion of cervix (blind pouch)
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Free edge of the broad ligament is the round ligament
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Blood supply to carnivore ovary and uterus
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What happens in the female after puberty with GnRH? Discuss both tonic and surge centers.
\* The tonic center controls basal levels of GnRH (higher than prepubertal female)--- the surge center controls preovulatory GnRH surge
\* low levels of oestradiol has a negative feedback on the tonic center BUT while puberty is approaching the negative feedback is weak, therefore GnRH release--\> FSH/LH release--\> higher oestradiol concentrations--\> if it reaches a certain threshold then there is a positive feedback on the surge center, which leads to a massive release of GnRH and tehrefore LH and therefore OVULATION
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Neurohormones vs. hormones- two examples of neurohormones
GnRH and oxytocin are neurohormes deposited directly through capillaries (also produced by the paraventricular nucleus of the hypothalamus)
vs. hormones (LH and FSH)- are substances that are produced by a gland and they act on (often remote) target tissues. Most hormones have relatively short half- lives
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What is an important fact about GnRH?
It is prone to downregulation if an individual is exposed to it for a prolonged period of time. e.g. GnRH implants. In females overtime FSH and LH release decreases while in males, sperm production decreases
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What hormones do the ovaries produce? What are they generally called? And where do their feedback loops go?
Oestrogen, progesterone, inhibin, oxytocin, relaxin, some testosterone
\* generally called Gonadal hormones
\* feedback loops with the hypothalamus and the pituitary
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What is the oestrous cycle? What is mean by just "oestrus?"
Oestrous cycle -series of predictable reproductive events, which continue through the adult female's life and are interrupted by pregnancy, lactation, (season in some species). Inadequate nutrition or unfavorable environmental factors and pathological reasons can also temporarily cease cyclicity.
Oestrus- heat
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What are the two phases of the oestrus cycle?
\* Follicular phase- dominated by a dominant follicle (or multiple with litter species) that produces oestradiol
\* Luteal phase- by a corpus luteum (or corpora lutea in litter species) that produce progesterone
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What happens in proestrus? Oestrus? Dioestrus?
\* Proestrus: formation of ovulatory follicles, increasing oestradiol (E2) secretion-- begins when progesterone (P4) declines as a result of luteolysis and terminates at the beginning oestrus.
\* Oestrus: sexual receptivity and peak E2 secretion (except in the dog) characterized by gradual progression to sexual receptivity in response to rising oestrogen levels.
\* Dioestrus: Longest stage. CL formation and rising progesterone levels. Period between ovulation and formation of corpora lutea. Luteinisation (cellular and structural remodelling of ovulated follicle). Sustained progesterone secretion, ends with luteolysis.
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What happens when luteolysis occurs?
Removes the negative feedback on the hypothalamus, therefore GnRH release in higher amplitudes and frequencies. FSH and LH are released in higher concentrations--\> promoting follicular development. When a dominant follicle is selected, it will produce inhibin leading to a decrease in FSH release.
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What are the 4 events of the follicular phase?
1. Gonadotropic release from AL of pituitary (FSH and LH= follicles.. and when threshold of GnRH is reached--\> more GnRH in a short period)
2. Follicular preparation of ovulation
3. Sexual receptivity
4. Ovulation
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Talk through this diagram
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Talk through this
Proestrus: as P4 drops, FSH and LH increase in response to GnRH. FSH and LH lead to production of oestradiol by ovarian follicles
Oestrus: dominant follicles produce oestradiol and inhibin. Inhibin suppresses FSH secretion and oestradiol leads to the stimulation of the surge centre in the hypothalamus: increase in GnRH, followed by an LH peak (FSH does not surge simultaneously beacuse of the negative feedback from inhibin).
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What are the four processes of antral follicles?
Recruitment: a cohort of follicles are selected and start growing
Selection: A few undergo atresia and some are selected
Dominance: one (in monotocuous species) reaches dominance and starts producing inhibin
Atresia: the other undergo atresia because of lack of FSH (due to negative feedback from inhibin)
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What occurs on account of the preovulatory LH surge?
\*Ovulation requires destruction of follicular tissue due to hyperaemia--\> oedema--\> elevated hydrostatic pressure (angiogenic factors have been found in follicles suggesting they control their own bloodflow)
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What happens during the luteal phase?
1. corpora lutea formation
2. production of progesterone
3. luteolysis
\*When the follicle ruptures and the fluid leaks out, blood vessels also rupture and fill the new cavity with blood--\> CORPUS HAEMORRHAGICUM forms.
\*\* theca interna and granulosa cells get through into folds and mix--\> they undergo luteinization (transform into luteal tissue). CL is a mixture of larget luteal cells (LLC), former granulosa cells, and small luteal cells (SLC), former theca interna cells. They are both steroidogenic, hence producing progesterone.
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What are the effects of progesterone?
Negative feedback on the GnRH neurons--\> less LH and FSH produced
\* positive effect on the endometrium (gland secretion increases, contractility decreases), cervix closes
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Why is the uterus necessary for luteolysis in most species? SO what happens with loss of uterectomy?
Uterus produces prostaglandin F2alpha that enters the uterine drainage, it then diffuses from the uterine ovarian vein into the ovarian artery and is transported directly to the ovary where it causes luteolysis
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What are the requirements for luteolysis?
Why does luteolysis happen?
\* presence of oxytocin receptors on endometrial cells
\* presence of a critical level of ovarian oxytocin
\* PGF2alpha synthesis by endometrium
\*\* one reason luteolysis occurs is that large lutein cells produce oxytocin as well. Oxytocin stimulates prostaglandin release from the endometrium???
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Talk through this diagram
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Oestrus cycle vs. Menstrual cycle
\* oestrus starts and ends with ovulation, whereas menstrual begins and ends with start of mens, OV in the middle of teh cycle
\* Oestrus: short follicular phase, long luteal phase and Menstrual: phases similar in length
\* Oestrus cycle: no shedding of endometrial mucosa, Menstrual: shedding of endometrial mucosa
\*Oestrus cycle: sexual receptivity to time of "heat", Menstrual: sexual receptivity not limited to any specific time
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What is the visceral vaginal tunic?
Covers the outer surface of each testis-- serosa-- only does not cover the testis where the epidiymis is attached.
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What is the tunica albuginea of the testis?
Dense irregular fibrous connective tissue which may contain smooth muscle, and is relatively inelastic... contains a vascular layer which carries major branches of the testicular vessels which are grossly visible externally because the VVT is thin.
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What is the rete testis?
In the mediastinum testis (concentration of connective tissue) contains a network of canals-- these connect the germinal or seminiferous tubules of the testicular parenchyma with the initial ducts of the epididymis at the cranial poles of the testis.
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What is the epididymis anchored to the wall of the scrotum via? How is the body of the epididymis attached? How long is the epididymis? What does it eventually become? Where does it originate?
"The ligament of the tail of the epididymis"
AND
the body is attached to the testis via the mesepididymis
\*\* the epididymis is 7 m in the dog and 80 m in the horse-- convoluted
\*\* eventually becomes the ductus deferens
\*\* epididymis originates as the rete testis
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What is the path of the ductus deferens?
\* leaves the epididymis--\> joins testicular vessels in the spermatic cord--\> inguinal canal into the abdominal cavity--\> ventral to the ureter then dorsal to the bladder to enter the genital fold--\> pass through the prostate gland in close proximity to each other--\> open into the urethra at the seminal colliculus .... it expands to form the ampulla in the ruminant, horse, and dog with MUSCOSAL and submucosal glands....
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What is the spermatic cord? Where does it run?
\* ductus deferens, testicular vessels, and nerves, and supporting mesenteries (mesorchium and mesoductus deferens (supports the testis and carries testicular vessels-- it is a fold of the peritoneum that continues through the inguinal canal) and visceral vaginal tunic)
\*\* spermatic cord extends from the deep inguinal ring to the testis
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What is special about the testicular vessels?
Adopt a special form within the spermatic cord-- the testicular a. winds through an extensive venous plexus called the pampiniform plexus. 7 m of artery in 10 cm of spermatic cord. This enables counter-current heat exchange and possibly testicular hormonal self regulation.
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What is the scrotum?
\* contains the testis, epididymis, and spermatic cords
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What are the 5 layers of the scrotum?
1. Skin and tunica dartos- thin with sweat glands, hair, connective tissue, elastic fibres, and smooth muscle
2. External spermatic fascia- fibrous connective tissue
3. Cremasteric Cremastic fascia- cup shape aponeurotic attachment for the cermaster m. which arises from the internal abdominal oblique m.-- which action is to alter the position of the testis relative to the body wall
4. Internal spermatic fascia- thin layer that supports the parietal vaginal tunic
5. Parietal vaginal tunic- serosal membrane lining each scrotal cavity and reflects scrotal contents at the mesorchium to become the visceral vaginal tunic
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What is the function of the testicles? What is key in testicles?
\* production of spermatogenesis and hormone production
\* very dependent on temperature- below core body temperature, whereas hormonal production is not as sensitive
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What are the mechanisms involved in thermoregulation of the testes to allow spermatogenesis?
1. Scrotal skin is exposed to free airflow, scrotal and testicular connective tissue is devoid of fat and larger blood vessels are located superficially-- abundant sweat glands
2. Action of cremaster muscle can alter position of the testis relative to the body- thus influencing scrotal skin exposure to cooling air
3. Specialized structure of the testicular vessels within the spermatic cord facilitates counter-current heat exchange- cooling arterial blood prior to entering the testis
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What are the 2 main sections of the urethra?
Pelvic- from the neck of the bladder to the ischiatic arch where it enters the penis (most species has the urethralis muscle-- smooth muscle to skeletal muscle later in life)
Penile (spongiose)- extends the length of the penis on the ventral aspect- surrounded by a sleeve of cavernous tissue (corpus spongiosum)
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What are the accessory glands of the male? Where are they?
\* ampullae
\* vesicular glands and ejaculatory duct
\* prostate- all species
\* bulbo-urethral glands- not in dog or cat
\*\* grouped around the pelvic urethra (castration leads to atrophy)
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What are the 2 bodies of the penis?
\* Corpus cavernosum penis- paired columns, the crura, of erectile tissue- firmly attached to ischiatic arch (form part of the root of the penis)--- with two main types (1) fibroelastic (S shaped- ruminants and pigs) (2) musculocavernous (abundant erectile tissue- horse and carnivores)
\* Corpus spongiosum penis- sleeve of erectile tissue with a connective tissue capsule-- starts at the bulb of the penis and expands to form the glans penis
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What are the 3 muscles of the penis?
1. ischiocavernosus mm. - surrounds the 2 crura of teh penis- pumps blood into the corpus cavernosum and positions penis during coitus
2. bulbospongiosus m.- envelopes the corpus spongiosus at the bulb of the penis-- circularly arranged muscle fibres (skeletal m.)-- pulses during ejaculation to assist in expulsion of semen
3. retractor penis mm.- smooth muscle from the caudal vertebrae- pass on either side of the anus (go as far as the glans in the musculocavernous type penis, stop at the sigmoid flexure of the fibroelastic type penis)-- retracts the penis back into the prepuce
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The 3 branches of the penis are? What do they branch from?
Branch from the internal pudendal arteries:
1. Artery of the bulb which supplies the corpus spongiosum
2. deep artery- supplies the corpus cavernosum
3. dorsal artery- to the glans
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Mechanism of erection
\* increasing blood flow to the cavernous tissues AND decrease in venous outflow
\*\* Walls of coiled arteries relax-- uncoil and fill with blood -- filling the cavernous tissue
\*\* compresses venous outflow
\*\*additional blood is pumped in via rhythmic contractions of the ischiocavernosus and bulbospongiosus mm.
\*\* post ejaculation-- helecine aa. contract and reduce blood inflow-- muscles and elastic tissue forces blood out.. retractor penis m. pulls back into prepuce
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Main differences between fibroelastic and musculocavernous penises?
\* Fibroelastic- little blood required-- essentially increases rigidity and enables protrusion via effacement of flexure, little change in length and width
\* Musculocavernous- much blood required- to achieve increased length, width, and rigidity
213
What is smegma?
An unpleasant smelling material that accumulates in a pig's preputial diverticulum (unique to the pig)-- which is desquamated epithelia and urine
\*\* in the horse- grey to black caseous smegma accumulates within the preputial cavity of the horse and may be found within the gossa of the glans penis-- sometimes forms a plug called a bean.
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Innervation of male repro?
Somatic:
\* Scrotum & prepuce: lumbar plexus, iliohypogastric, ilioinguinal and genitofemoral nn.
\* Vaginal tunic & cremaster m- genitofemoral n.
\* Penis & prepuce- pudendal n.
\* Bulbospongiosus, ischiocavernosus, and retractor penis mm.- deep perineal and caudal rectal nn.
Autonomic:
\* Testes- testicular plexus (accompanies testicular vessels)
\* Accessory glands, urethra, and penis- pelvic plexus
215
Phases of spermatogenesis-- what is it? What are they?
development of spermatogonia into spermatozoa (50-74 days)-- requires optimal temperature and complex interaction of hormones-- when spermatozoa are released they lack mobility-- the ability is acquired during passage through tubular tract
1. Spermatocytogenesis- spermatogonia give rise to spermatocytes
2. Meiosis- spermatocytes give rise to spermatids
3. Spermiogenesis- spermatids transform into spermatozoa
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Clinically important aspects of the embryology of the male reproductive system?
1. presence of Y chromosom in cells of the gonadal ridge is necessary for development of the testis. Testis Determining Factor (TDF) is probably the same as the sex determining Y gene (SRY) located on the Y chromosome. GENE SWITCHES ON = GONAD--\> TESTIS
2. Mesonephric ducts develop into epididymis, vas deferens, and seminal vesicles
3. Prostate and bulbourethral glands develop from the urogenital sinus
4. The genital tubercle and genital folds become the penis and prepuce (separate via androgens at work)
5. Genital swellings become scrotal pouches
6. Vestigial structures of importance are meonephric tubules and the uterus masculinus
7. Descend of testes is complete at birth in domestic animals.
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What is secreted by the pineal gland? How does it impact the male? What is the number one cause in decrease of pineal gland secretions?
Melatonin-- which exercises an inhibition over male sexual activity. Increases at night... melatonin influences the GnRH pulse generating system in the CNS.
\* Under nutrition is the number one cause of change in sensitivity of the neuroendocrine-reproductive system to the pineal secretions
\*\* in all species more dark = more melatonin secretion
218
What happens with continuous treatment of adult rams with GnRH?
\* stimulates and then eventually suppresses gonadotrophin secretion and hence gonadal function
\*\* FSH and LH are continuously released into the blood stream from the anterior pituitary via GnRH
219
WHat can modify GnRH synthesis and release?
Environmental factors such as light-- which impacts melatonin-- therefore impacting GnRH
220
What does LH do in a male? What does FSH do in a male
\* LH stimulates the production and release of testosterone due to Leydig cells of teh testis (proportional release) & direct effect on spermatogenic tubules (Sertoli cells and may control the rate at which they release spermatozoa)
\* FSH acts synergistically with LH-- important in developing testis. FSH direct action on germinal epithelium. FSH stimulates the production of androgen binding protein (ABP) by Sertoli cells so that the steroid hormone accumulates at its site of action in the tubules. ABP transports testosterone in the rete testis and epididymil fluid... FSH and LH are responsible for the number of Sertoli cells laid down in the testis in early life (before 20 weeks in the bull)
221
What does inhibin do in the male and female?
Acts with testosterone in the male to suppress FSH production (negative feedback on the hypothalamic-pituitary system)
222
Testosterones role?
Induce development and maintain function of the male genitalia... spermatogenesis. Male sexual behaviour. Increases aggression, loss of hair from the scalp, growth of facial hair. Stimulates sebaceous glands. In the boar stimulates a pheromone from the salivary gland that excites the female. Controls growth and shedding of antlers in malde deer. And development of coloured plumage in male birds. Deepens the voices of tom cats (and odour of tom cat urine via lipid secreted in the kidney).
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What are the key hormones in spermatogenesis?
LH, FSH, testosterone, and inhibin
\* Thyroxine-- resulting from general effect on metabolic or energy controlling processes
\* Adrenals secrete androgens and oestrogens (hence stress influences)
\* Oestrogens secreted by Sertoli cells or Leydig cells
\* Prolactin-- light photoperiod influences release-- if deficiency can be sterile
224
what inhibits sperm metabolism?
testicular fluid- by selective resorption of some of the constituents in the epididymis the fluid becomes more inhibitory to spermatozoa e.g. in the full the potassium concentration is higher in the head than in the rete testis.. The sodium potassium ratio changes in the epididymis
225
Where are fertile spermatozoa stored?
Epididymis (tail)
226
What is semen?
\* Spermatozoa with seminal plasma
227
How is seminal plasma produced and what is its composition and function?
\* epididymis stores sperm-- contributes glycerylphosphorylcholine and enzymes, seminal vesicle-- potassium and fructose, proteins, PGs, ampullary glands- similar to seminal vesicle, bulbourethral glands- sialoprotein, galactosamine, prostate- acid fluid with proteolytic enzymes, zinc, copper
228
What kinds of metabolism are spermatozoa capable of? What does this do for spermatozoa?
Oxidative metabolism (respiration) and anaerobic glycolysis. This makes them adaptable to the different environmental conditions they meet between the testis and oviduct.
229
HOw does the seminal plasma and spermatozoa combine?
Flow of fluid in the seminiferous tubules, active contraction of the tubules bring the sperm to the epididymis.
230
What happens in ejaculation? How is it kept from going into the bladder?
\* Series of coordinated contractions
\* Muscular tissue in the walls of the epididymis and vas deferens undergo peristaltic contraction--\> sperm are forced into the pelvic urethra.
\* prevented from going to the bladder by the urethral crest and closure of the bladder sphincter (not active during sexual rest, sperm are found in the bladder)
\*\* accessory gland secretion is brought forth to the pelvic urethra by muscular contractions of the walls of the glands
\*\* final discharge is via rhythmic contractions of the urethral muscle, the bulbo cavernosus and the ischio-cavernosus muscles
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What is the most important organ contributing to male repro function?
Hypothalamus-- repro activity, growth, lactation, stress reactions, temperature regulation
232
How does sperm travel?
\* testis to the epididymis--\> vas deferens which widens to form the AMPULLA--\> seminal vesicles secrete seminal fluid (except in the dog)
233
Where would you palpate the head of the epididymis in the bull? Where is the tail of the epididymis in the stallion, boar, and dog?
234
Draw a bull. Put in all his reproductive organs. Colour organs of different embryological origin different colours.
