VRB vets only Flashcards
(228 cards)
1
Q
What is the site of sperm production?
A
The paired testes
2
Q
What else do the testes produce?
A
Testosterone and other hormones
3
Q
What are the layers surrounding the testis?
inner to outer
A
Fibrous capsule- the tunica albuginea Visceral peritoneum Parietal peritoneum Internal fascia External fascia Dartos (fibroelastic tissue and smooth muscle) Skin
4
Q
Where does spermatogenesis occur?
A
Seminiferous tubules
5
Q
Where are the rete testis found?
A
The mediastinum
6
Q
Main role of leydig cells
A
Steroid formation
7
Q
How do the rete testis penetrate the tunic?
A
Via the efferent ducts
8
Q
Where does the epididymis empty?
A
The deferent duct, and then up via the spermatic cord
9
Q
Where do the peritoneal coverings come from?
A
The vaginal process- an out pocket from the abdomen leaving through the inguinal ring
10
Q
What does the cremaster muscle do?
A
Pulls the testes towards the abdomen
11
Q
What two ligaments attach to the epididymis?
A
The proper ligament and the ligament of tail
12
Q
Where does the proper ligament lie?
A
Between the epididymis and the testis
13
Q
Where does the ligament of tail lie?
A
Between the epididymis and the parietal peritoneum
14
Q
What is the mesorchium?
A
The visceral peritoneum supporting the testicular vessels and the deferent duct.
15
Q
What is the mesoductus?
A
The part of the visceral peritoneum that covers the deferent duct
16
Q
What is the space between the parietal and visceral peritoneum called?
A
The vaginal cavity/ space
17
Q
Which species has a testicular bursa?
A
Horse- the body of the epididymis is not closely attached to the testis
18
Q
Open castration
A
Testes are removed enclosed in the parietal peritoneum.
Ligate cord, cut distal to ligature.
May decrease risk of complications
Indicated when testes removed due to disease.
19
Q
Closed castration
A
Parietal tunic is opened and left behind.
Incise close to visceral peritoneum.
Opens peritoneal cavity.
Simpler dissection than closed.
20
Q
Restraint for equine castration (standing)
A
Performed under sedation and local analgesia.
Avoids risk and cost of GA
21
Q
Restraint for equine castration (general anaesthesia)
A
Easier for the surgeon.
Different risks though
22
Q
Bloodless castration methods (2)
A
Burdizzo clamp:
- Severs testicular blood vessels but not scrotal ones
Elastrator rings:
- Cut off blood to testis and scrotum
23
Q
Chemical castration (4)
A
GnRH vaccines:
- GnRH susceptible to antibody in the hypophyseal portal system
- virtually all GnRH can be bound and neutralised
Chronic progestagen administration:
- suppression of GnRH and LH release
GnRH antagonists:
- Suppress release of gonadotrophins by occupying GnRH receptors
Chronic high dose GnRH agonists:
- In some species, initial hypersection is followed by pituitary dissemination and decrease Gn release
24
Q
What can elevation of scrotal temperature cause?
A
Inhibition of sperm production
25
Where in the male reproductive system is there counter current flow?
Between the testicular artery and vein
26
Testicular thermoregulatory mechanisms
- Counter current flow
- Thin skin
- Often hairless
- Copious sweat glands
- Little subcutaneous fat
- Pendulous scrotum away from abdominal wall
- Dartos and cremaster muscles
27
What is the gubernaculum?
A fibromuscular mesenchymal core. It runs between testes and runs through the inguinal ring into scrotum. It shortens and helps to pull the testes ventrally during development. It regresses once the testes exit the abdomen.
28
What hormones are involved in testicular descent?
Testosterone, INSL3 and Mullerian inhibiting substance.
Androgens act on the suspensory ligament, allowing it to elongate.
INSL3 matures and stabilises the gubernaculum.
29
What is cryptorchidism?
Hidden testes- can be uni- or bi-lateral.
30
Timing of testicular descent in different species
Ruminants: mid-gestation
| Dog, cat, horse: around parturition
31
What is weird about testicular descent in rat, mole, hedgehog and bat?
The testes can ascend back into the abdomen outside of breeding season and reappear in scrotum during the breeding system.
32
What is true cryptorchid?
Testis on normal route, but incompletely descended.
33
What is ectopic cryptorchid?
Testes in abnormal position.
34
Inguinal hernia
- Herniation of intestine through the inguinal canal into the scrotum
- Relatively common in horse and pig
- A surgical emergency if there is brutal strangulation
- The testicle on the affected side usually has compromised vascular supply and is generally removed
35
Indirect inguinal hernia
The gut stays within the parietal vaginal tunic
36
Direct inguinal hernia
The gut ruptures the parietal tunic
37
What is the spermatic cord?
Provides connection and suspends the testes from the abdomen.
38
What makes up the spermatic cord?
Parietal vaginal tunic, visceral vaginal tunic, deferent duct, testicular artery and vein, artery of deferent duct, lymphatics, testicular nerve to testis
39
What are the edges of the deep inguinal canal?
The free caudal edge of internal abdominal oblique
40
What are the edges of the superficial inguinal ring?
A slit in external abdominal oblique.
41
What is the vesicogenital pouch?
A fold of peritoneum gives rise to a space between the
| genital fold fold and the bladder
42
What is the rectogenital fold?
A layer of peritoneum creates a pouch between the genital fold and the rectum.
43
Arterial supply to the testes
Comes directly from the aorta, close to the renal arteries (testicular or internal spermatic artery).
44
Where does the testicular vein drain?
Directly to the caudal vena cava
45
What is the pampiniform complex?
The tortuous testicular veins (for heat and hormone exchange)
46
What does the internal iliac artery supply?
The deferent duct, the epididymis and anastomoses with the testicular artery.
47
Testicular innervation
Sympathetic nerves from fourth, fifth and sixth lumbar ganglia.
48
Innervation and blood supply of the scrotum
Blood supplied by the external pudendal artery and vein. Innervated by the genitofemoral nerve and the perineal branch of the pudendal nerve.
49
The ampulla
Not really an accessory gland as it isn't a distinct structure. The thickened terminal wall of the vas deferens. It has very glandular walls causing an increase in diameter but not in lumen.
50
The seminal vesicles
Paired structures located dorsolateral to the neck of the bladder. They secrete an alkaline fluid, rich in fructose and usually open into the vas deferens, but into the urethra in the boar.
51
The prostate gland
The only accessory gland present in all domestic species. Its secretions assist in providing the optimum environment for sperm survival and motility. It surrounds the urethra distal to the entry of the vasa deferentia and discharges through many small ducts.
52
Bulbourethral glands
Found in the dorsocaudal aspect of the proximal urethra. They produce a mucous secretion that has a buffering effect and they open into urethra on its dorsal aspect.
53
What male accessory sex glands do horses have?
- Prominent ampulla
- Bladder like sacs of seminal vesicles
- Two lobes of prostate gland joined by isthmus
- Bulbourethral gland that discharges through multiple pores
(all)
54
What male accessory sex glands do bulls and rams have?
- Ampulla
- Large, lobulated seminal vesicles
- Prostate that surrounds urethra
- Relatively small bulbourethral gland
55
What male accessory sex glands do boars have?
- No ampulla
- Very large seminal vesicles
- Small, irregular prostate gland
- Very large bulbourethral gland
56
What male accessory sex glands do dogs have?
- No ampulla
- No seminal vesicles
- Bilobed prostate
- No bulbourethral gland
57
What male accessory sex glands do cats have?
- No ampulla
- No seminal vesicles
- Prostate surrounds urethra and distal vasa deferentia
- Present bulbourethral gland
58
Three parts of the penis
The root, the body and the glans
59
The two types of penis in domestic animals:
The musculocavernous penis:
- Horse and carnivores
- Low connective tissue content (flaccid when not erect)
- Engorgement of the erectile tissue with blood leads to an increase in size and stiffening
The fibroelastic penis:
- Boar and ruminants
- High connective tissue content and so always firm
- Increase in length without changes in diameter, occurs due to straightening of the sigmoid flexure
60
Glans species differences- horse
Horse (use diagrams): Dorsal process, collum glandis, corona glandis, urethral sinus, fossa glandis, urethral process, inner and outer prepuce
61
Glans species variation- bull
Flattened dorsoventrally, pointed and twisted.
External urethral orifice is quite narrow.
Lies at the end of a urethral process which is fused with the galea glandis.
62
Glans species differences- ram
Urethral process (sort of hooked), glea glandis, corona glandis, raph glandis.
63
Glans species differences- boar
Spiral shaped
64
Glans species differences- cat
Backward pointing barbs
65
Glans species differences- dog
Rounded, enlarged bulbus glandis and very long cylindrical pars longa
66
Corpus cavernosum
Consists of paired erectile structures with large venous spaces. It is divided by a septum in carnivores but essentially a single compartment as the septum is incomplete. It divides in the root to form the crura.
67
Corpus spongiosum
A tubular erectile structure surrounding the urethra. It expands to for both the glans and the bulb of the penis. Function seems to be to prevent the urethra closing under the pressure of the corpus cavernosum.
68
Tunica albuginea (penis)
The fibroelastic sheath. Trabeculae of connective tissue radiate inwards from it to support the vascular spaces.
69
The root of the penis
Comprises the bulb and the crura.
Crura: separate, proximal portions of the corpus cavernosum
Bulb: broad proximal portion of the corpus spongiosum.
Here the ischio-cavernosus muscle encloses the crura.
The penis is attached to the ischial arch by the crura. The urethra passes over the ischial arch between the crura and then curves forward.
70
Body of the penis
Section between the junction of the crura and the glans. Attached to the pelvic symphysis at its base by the suspensory ligament of the penis.
71
Glans penis
The distal end of penis. It's erectile tissue derived from the corpus spongiosum. It shows considerable inter-species variation.
72
Os penis (baculum)
Found in the penis of carnivores, and the majority of mammals. (Dog, cat and rat out of domestics).
In the og the ventral surface has a groove for the urethra.
73
The prepuce (sheath)
Forms a cutaneous sheath over the penis. Inner lamina is continuous with the skin of the glans. The prepucial orifice is the external opening of the prepuce.
74
Equine prepuce
Double prepuce- due to degree of lengthening of the penis on erection. Clinical relevance in testing for STI Contagious Equine Metritis.
75
Ischio-cavernosus
O: tuber ischia and adjacent sacrosciatic ligament
I: crus and adjacent body of penis
Encloses the crus and lies within a depression in the semimembranosus muscle. Pulls the penis against the pelvis compressing its dorsal veins and so assists in producing and maintaining erection.
76
Retractor penis
O: continuation of the suspensory ligaments of the anus (attached to the external anal sphincter)
I: Tunica albuginea near glans
Composed of smooth muscle, its action is to withdraw the penis into the sheath after erection or protrusion.
77
Urethral muscle
Found around the pelvic part of the urethra (not actually a penis muscle). Its forceful contraction is important in ejaculation and it also has a role in voiding the last of the urine in micturition.
78
Bulbocavernosus muscle
A continuation of the urethral muscle around the extra-pelvic portion of the urethra. It varies in its degree of extension between species. Its contraction empties the urethra.
79
Ischio-urethral muscle
In the horse, it arises on the crus and ischial arch, passes forward to the urethral muscle.
In the dog, it arises on the tuber ischii and ends on a fibrous ring on the pelvic symphysis, encircling dorsal veins of penis. It is formed of small bands that may assist erection by pressing on the dorsal veins of the penis.
80
Blood supply to the penis
1. Internal pudendal artery supplies the artery of the bulb of the penis
2. Internal pudendal also supplies deep artery of the penis
3. External pudendal artery supplies the dorsal artery of the penis
Veins form rich plexus dorsally and laterally on the penis and drain via the external and internal pudendal veins.
81
Testicular artery
A branch of abdominal aorta, close to kidney.
82
Innervation of the penis
Derived from the pudendal nerves and pelvic sympathetic plexus. The parasympathetic NS is responsible for erection and the sympathetic for ejaculation.
83
Innervation of the scrotum
Genitofemoral n. and the perineal branch of the pudendal n.
84
Innervation of prepuce
Mainly genitofemoral n. with the dorsal nerve of penis from the pudendal n. supplying the penis and also a little skin at the distal extremity.
85
Innervation of testes
Sympathetic nn. from L4-6, entering with testicular artery; dartos muscle supplied from superficial perineal nerve.
86
Formation of gonads (origins)
Form in sublumbar region from intermediate mesoderm
87
Where do the wolffian ducts
Form from urinary ducts of mesonephros
88
Ovary structure
Similar in all mammals
- Outer peritoneal coating
- Fibrous tunica albuginea (thinner than in testes)
- Cortex: follicles and their derivatives (oocytes, granulosa, theca and luteal cells); interstitial cells; stroma
- Medulla/ hilus: connective tissue, nerves, vasculature, lymphatics
89
Ovary- species variation
General shape dominated by how many in a litter
Sow: mulberry ovary (multilobar) to produce around 16 eggs
Mare: Ovary is 'inside out', cortex is inside the medulla. Ovulation is always form the medial 'ovulation fossa' towards which maturing follicles migrate.
90
5 parts of the oviduct
1. Fimbrae (some species)
2. Infundibulum
3. Ampulla
4. Isthmus
5. Intramural section
91
Fimbrae of oviduct (some species)
Slightly mobile fingers that are involved in grasping newly ovulated cumulus-oocyte complexes. Not a big feature in the domestic species.
92
Infundibulum of the oviduct
Cone like entrance to oviduct
93
Ampulla of oviduct
About first 1/2 of oviduct, thin muscle, very folded epithelium
94
Isthmus of oviduct
Thick muscular layer, fertilisation occurs around ampulla/ isthmus junction
95
Intramural section of oviduct
Where it passes through the uterine wall
96
Four layers of the oviduct
- Serosa/ visceral peritoneum
- Muscularis (outer longitudinal, inner circular)
- Submucosa
- Epithelium- columnar, secretory, ciliated
97
Varied location and structure of female internal structures
Carnivore: long horns, simple long cervix, so ovaries up near kidney
Horse: Short horns, simple short cervix, large, indented ovaries close to ilium.
Pig: very long horns, cervical caruncles, ovaries more ventrally
Ruminant: Rams horn shape, cervical rings, uterine caruncles
98
Differential morphologies of the uterus
Duplex (rabbit): no fusion at all
Bicornis (most domestic animals) central uterine body/ fused
Simplex (humans): no uterine horns- all fused
99
Uterine structure
Much of the epithelium (endometrium) is glandular, the muscularis is complex
100
Uterus specialisations of ruminants
Specialised sites for attachment of the embryo: the caruncles- non-glandular protuberances- are often highly pigmented.
101
Canine pro-oestrus
Uterus leaks blood by diapedesis (not menstruation)
102
Uterine prolapse
Most often seen in ruminants, usually after birth. Entire uterus turns inside out and so hangs out.
Treat by putting osmotic sugar solution on to make it contract down, and push back in
103
Cervix
Muscular, fibrous, mucus secreting.
| Uterus sealing, sperm storage (?), ferguson reflex at birth
104
Differential cervical structure
Mare: often slightly open
Carnivore: Longer, less open
Ruminant: rings
Sow: cervical caruncles
105
Vaginal structure
Dual embryology:
- Cranial is fused Mullerian ducts (meso-)
- Caudal is canalised sinovaginal bulb (endo-)
- Cranial is covered by serosa
- Caudal is retroperitoneal
- Cow laproscopy via less vascular craniodorsal wall
- Needs to be physically resilient for copulation
- Stratified squamous, with Bartholin's glands
- Non-sterile, with normal flora
- Secretes pheremones
- Orgasm related to sperm propulsion?
106
Vagina and vestibule
Cervix: Porto vaginalis, fornix (not pigs)
Vagina: Hymen (separates from vestibule)
Vestibule: Urethral meatus, suburethral diverticulum (ruminants and pigs), rima vulvae
107
Suspensions of the female reproductive tract
Rectum: mesorectum, produces the pararectal fossa
Uterus: Broad ligament- a double fold of peritoneum with blood vessels, nerves and smooth muscle, the two horns are held together by the intercornual ligament
Bladder: Lateral vesical ligaments and ventral vesical ligament (urachus)
108
Three parts of the broad ligament
Mesovarium= suspensory ligament (elastic in cats)
Mesosalpinx
Mesometrium
109
Round ligament
Ventral broad ligament --> ?inguinal canal
persists in some species but not others
110
Ovarian bursa
In some species there is a fold of peritoneum between the mesovarium and mesosalpinx.
Present in pigs and ruminants, not really seen in horses. May be partial (carnivores), or completely enclose the ovary (mice).
111
Arteries to the internal female reproductive structures
(Utero)ovarian artery- from aorta or renal artery
Anastamoses up the uterine horns
(Middle) uterine artery- from vesical or ext. iliac (largest in ruminants 'fremitus', absent in carnivores)
Vaginal/ caudal uterine artery- from urogenital artery
112
Innervation of internal female reproductive structures
Parasympathetic supply via pelvic nn.; sympathetic in broad ligaments from hypogastric nn.
113
The four mammalian fetal membranes
Yolk sac, allantois, amnion and chorion/ trophoblast
114
Where does the haemotrophic placental exchange occur?
Wherever the yolk sac OR allantois contact the trophoblast
115
Mammalian differences in placenta
In most marsupials, the yolk sac + trophoblast 'choriovitelline' placenta is the most important.
In some eutherians (e.g. ruminants) only an allantois + trophoblast 'chorioallantoic' placenta forms.
In other eutherians (e.g. horses) an initial choriovitelline placenta is replaced by chorioallantoic one.
In other eutherians (e.g. mice), both placentas may persist and function until birth.
In all eutherians, the chorioallantoic is the most important (or only) placenta during most of pregnancy.
116
Fetal membrane connections to gut
1. Yolk sac connects to endoderm of midgut (often disappears early)
2. Allantois connects with endoderm of bladder via urachus- may remain patent e.g. foals
3. Buccal plate breaks down --> mouth opens into amniotic cavity
117
Fetal shunts in circulation
Two R-->L shunts in heart:
Foramen ovale RA-->LA
Ductus arteriosus PA-->Aorta
Umbilical vv. (oxygenated)--> HPV --> through liver as ductus venosus --> CdVC --> right atrium
Iliacs --> vesical (bladder) aa. --> umbilical aa. (deoxygenated)
118
Different types of twins
Dizygotic 'fraternal': as different as normal siblings
Monozygotic 'identical':
- Dichorionic, diamniotic
- Monochorionic, diamniotic
- Monochorionic, monoamniotic (could be conjoined)
119
Placental types- membranes
- Choriovitelline (chorion + yolk sac): some reptiles and most marsupials
- Choriovitelline, then chorioallantoic: horse, carnivores, rodents (yolk sac persists)
- Chorioallantoic: some reptiles, ruminants, pigs
120
Placental types- shape
- Discoid: humans and rodents
- Cotyledonary: ruminants
- Zonary: carnivores
- Diffuse: equids, pigs
121
Placental types- implantation
- Central 'superficial': ungulates
- Eccentric: carnivores, rodents
- Interstitial 'invasive': humans
122
Placental types- cell layers
- Epitheliochorial: ungulates, prosimians (6 layers)
- Endothelialchorial: carnivores, pinipeds (4 layers)
- Haemochorial: simians, rodents, lagomorphs, insectivores
123
Placental types- surface area
- Folded: pig
- Lamellar: carnivores
- Villous + crypts: equids, ruminants, humans, rodents
124
Placental types- dehiscence
- Non-deciduate: domestic animals
- Deciduate: humans
- Contra-deciduate: moles
125
Placental types- relative capillary flow
- Counter-current: horse, rabbit (efficient)
| - Cross-current: ruminants, carnivores, human
126
Pig placenta
Chorioallantoic, diffuse, epitheliochorial, central, folded, non-deciduate
Maternal and fetal epithelia closely apposed over most of the placenta.
Chorioallantois also forms areolae- regions of histotrophic placentation (non direct blood-to-blood.
127
Carnivore placenta
Choriovitelline then chorioallantoic, zonary, endotheliochorial, eccentric, lamellar/ labyrinthine, deciduate, cross-current.
Marginal haematoma- green border- haemophagous zone.
Vestigial yolk sac.
128
Horse placenta
Choriovitelline then chorioallantoic, diffuse, epitheliochorial, central, villous, non-deciduate, counter-current.
Spherical conceptus.
Chorioallantois = red membrane
Allantoamnion = white membrane
After birth check that the red membrane only has one hole.
Sites of endometrial cups- portions of chorionic girdle (fetal tissue) which invade and secrete eCG.
Although diffuse, there are microcotyledons.
129
Ruminant placenta
Chorioallantoic, cotyledonary,(syn)epitheliochorial, central, villous, non-deciduate, cross-current
Fetal cotyledon + maternal caruncle = placentome
Bovine caruncle is convex, ovine caruncle is concave.
130
What is a freemartin?
Some but not all mixed sex fraternal twins of cattle:
- Vascular anastomoses between placentas
- Masculinisation of heifer calves by androgens
- Infertile- vagina may be very short
- Also can exhibit bone marrow chimerism
131
Mammary development
Develop along the milk line
Teats or nipples form as ingrowths of surface ectoderm which then canalise.
These ramify to form a discrete system of branching ducts.
132
Ducts per teat in different species
```
Ruminants 1
Horse, pig 2
Cats 6?
Dogs 12?
Humans >15
```
133
Location of teats
Tethytheria (elephants, sea cows etc.): Axillary
Primates: Pectoral
Ruminants and horses: Inguinal
Pigs: Pectoral, abdominal and inguinal
Dogs, cats, rabbits: Axillary, pectoral, abdominal, inguinal
134
Which animal has the most teats?
Multimammate rat (36)
135
Anatomy of a cow udder
A consolidation of more than one mammary gland- 4 'quarters' in cattle.
136
Anatomy of cow udder- suspension
Lateral laminae:
- collagenous
- suspended from fibrous sheet attached to ventral pelvis and prepubic tendon
Medial laminae:
- elastic extension of tunic flava
- lengthens as udder fills--> teats point laterally
- separated by loose connective tissue- used surgically
137
Anatomy cow udder- cisterns and ducts
Most gland appears homogenous but there are ducts and sinuses that aren't.
Varicose ducts lead to gland sinus (2100ml) leads to teat sinus.
Lactiferous sinus = milk sinus = GS + TS
138
Anatomy of the teat sinus
Submucosal venous plexus- semi-erectile.
Mucosa- often ridged
Connective tissue with venous plexi, smooth muscle.
Papillary duct (streak canal) and orifice with smooth m. sphincter.
139
Anatomy cow udder- arteries
External pudendal a. via inguinal canal.
Ventral perineal a.
140
Anatomy cow udder- veins
External pudendal v. via inguinal canal
Caudal superficial epigastric vv. valves fail during lactation. It anastomoses with cranial superficial epigastric to form the milk vein.
Ventral perineal v.
141
Anatomy cow udder- lymphatics
Superficial visible draining caudodorsally.
--> 2 superficial inguinal nodes (supramammary)
--> deep inguinal nodes via inguinal canal
142
Anatomy cow udder- nerves
Three sources:
- L1 and L2 to cranial surface
- Genitofemoral L3/4 via inguinal canal to much of ventral surface
- Pudendal n. S2-4 via perineum to caudal surface
Can be blocked for surgery; also sensory arm of milk ejection ('let down') reflex
143
Mammary anatomy- sheep and goat
- Two quarters
- More pronounced median groove in goats
- No papillary duct sphincter in sheep
144
Mammary anatomy- horses
- Two quarters- surprisingly small
- Elastic and collagenous laminae as ruminants- prominent median groove
- Thin, dark, almost hairless
- 'Wax up' soon before parturition- a deposit of sebum and colostrum
145
Mammary anatomy- pigs
- 7 pairs of glands not really joined, but occasionally called an 'udder'
- more cranial glands appear smaller but may secrete more milk (bitch similar)
- neonates have marginal tongue papillae, which may improve the seal on the teat (puppies similar)
146
Mammary anatomy- dogs
10 glands supplied by:
| - caudal superficial epigastric
147
Mammary anatomy- rabbits
Usually 8 glands, occasionally 10
148
Mammary anatomy- males
Present in many but not all species:
- abdominal in carnivores and boars
- scrotal in ruminants
- preputial in stallions (uncommon)
- not present in buck rabbits or male rats
149
Mammary immunology
- First milk secreted is colostrum
- High content of immunoglobulins (IgG monomer > IgA dimer > IgM pentamer)
- Secreted by a huge infiltration of lymphocytes which reach the mammary gland via blood from the peyers patches (?)
- This is 'maternal acquired passive' immunity
- IgA lines gut epithelium, others areabsorbed by specific FcR- mediated endocytosis in the SI
150
How does colostrum differ from normal milk
- Looks yellow
- Higher protein
- Lower fat
- Higher Na+
- Higher Cl-
- Higher FS vits
- Lower WS vits
Colostrum itself induces 'closure'- the inhibition of its own uptake mechanism.
Later milk still contains Ig, but relatively more IgA
151
How do female animals survive reproduction?
Breeding and growing up are the most risky energetically demanding things mammals can do.
Hormones are the means by which female mammals attune their reproductive activity to the environment.
152
What reproductive decisions do females make?
- When to start breeding- puberty
- Which males to breed with- sexual selection
- When to breed- seasonality, cyclicity
- How many offspring- litter size, frequency
(- When and whether to cease breeding- senescence)
153
Cows- follicle selection
- Ovarian follicles are continually recruited from the stock of primordial follicles
- Stimulated to grow and develop by pituitary FSH, feedback on with E and inhibin
- Follicular waves
- Eventually larger follicles develop LH receptors
- The number of follicles reaching this stage determines: ovulation rate, litter size, maternal drain, maternal and infant life and death
154
Positive feedback by follicles
The follicles grow and eventually plasma [E] reaches a threshold. This feeds back positively on LH pulse frequency (hypothalamus) and amplitude (pituitary).
LH pulses start to overlap and summate --> runaway LH surge --> oocyte maturation, ovulation and luteinisation. An accompanying surge of E affects the brain to cause oestrus.
155
What is ovulation?
A structural change in the follicle
156
What is luteinisation?
Biochemical change in the follicle. Follicular cells hypertrophy, infill the follicle, and secrete P
157
Ovulation and luteinisation in relation to each other
They occur in parallel- some P is produced before ovulation. Yet they can occur independently- e.g. in ovarian cysts
158
What is the corpus luteum?
A solid temporary endocrine organ secreting P for most of the cycle- the luteal phase
159
Luteolysis in cows
Cows are polyoestrus, so once the putative conceptus has had time to announce its presence, the CL must be destroyed. Destroyed by pulses of endometrial PGF2alpha- in a positive feedback interaction with luteal oxytocin pulses.
160
How does PGF2alpha reach the corpus luteum?
Cannot reach the CL via the systemic circulation, as it is destroyed in the lungs. It reaches the CL via direct counter-current exchange: ovarian vein (blood from uterus) --> ovarian artery (blood to ovary)
161
Recognition of pregnancy in cows
- Pre-implantation anti-luteolysin
- Interferon-tau: acts locally across a tiny distance to supress endometrial OTR expression. So it breaks the the PG
- A few genes closely related to alpha- and beta- interferons OT feedback loop and prevents luteolysis.
162
Cycle of the ewe
Show more seasonality than domestic cattle. Typical temperate 'short day breeders'. Cycle mechanisms similar to cattle.
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Seasonality influences
- Photoperiod
- Weather
- Nutrition
- Horizontal/ vertical migration
- ?lunar cycle
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Seasonality: melatonin
- Some non-mammalian species also have a pineal eye for direct detection of light levels
- At night pineal secretes melatonin, and indoleamine
- Melatonin used artificially in sheep to alter breeding period e.g. regulin skin implant for both sexes in sheep
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Seasonality: effects
Autumn --> longer nights --> more melatonin
- Acts directly and by inducing seasonal cycles of prolactin and thyroid hormones
- Many targets- metabolic, appetite, pelage
- Activates reproductive system by reproducing sensitivity of hypothalamic/pituitary to oestrogen negative feedback
166
Senescence
Not seen in most mammals- cycle until death.
Cessation of cycling in women and killer whales (menopause):
- remaining follicles unresponsive to gonadotrophins
- i.e. not related to hypothalamus/ pituitary sensitivity
167
Cycles of nanny goat
- Derived from middle eastern goat (Bezoar)
- Browser not grazer
- Intermediate seasonality- short day breeder in temperate zones, climate induced in tropics
- Very vocal in oestrus, discharge too
- CL essential for P secretion throughout pregnancy
- Very prone to pseudopregnancy- maybe because they're induced ovulators
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Cycles of sows
- Derived from wild boar
- Limited evidence of remaining seasonality
- Very high ovulation rate/ litter size, embryonic death is an important factor in litter size
- Oestrus is evident- restless, prick ears, frequent urination, vulval swelling, stand to pressure
- PRL is an important luteotrophin unlike other ungulates
- PGF2alpha is the main luteolysin
- MRP factor unknown
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Retained seasonality of mare
- Harsh natural environment
- Long day breeder, peak fertility at midsummer
- Opposite response to melatonin vs sheep
- Conflicts with aging system of the jockey club, want foals to be born as close to Jan 1st as possible
170
Control of 'litter size' in the mare
- Twinning is rare
- Very tight control of FSH E, inhibin feedback
- Live twins often not viable
- Even if one dies it often debilitates the other
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Oestrus behaviour of the mare
- Usually requires presence of male-'teaser'
- Obvious 'straddling, winking, and urinating'
- Donkey very different
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Luteolysis and MRP in mares
- PGF2alpha is luteolytic, but only variably so
- PGF2alpha analogues cause adverse side effects in horses
- MRP signal unknown
- The conceptus 'fixes' after 16 days, full implantation at 35 days before that time it migrates repeatedly from horn to horn- releasing a factor?
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Pregnancy endocrinology in mares
- Fragments of chorionic girdle invade under the endometrium at day 35 to form endometrial cups
- These secrete eCG from day 35-100
(similar to LH)
- This is not MRP- too late to arrest the cycle
- Induces and supports a crop of new ovulations- multiple 'accessory CLs'
- For much of pregnancy, the hormonal milieu is dominated by a complex mix of E, not P
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Seasonal mono-oestrus in bitches
- One oestrus per season, no 'cycles', no MRP
- Most not attuned to time of year
- Since pregnancy < inter- oestrus interval, it does not perturb the pattern of intermittent ovulation
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Gametes in bitches
- Ovulate a primary oocyte still arrested in meiotic prophase I, rather than metaphase II
- Ovulations may be spread over 48 hours or more and..
- Sperm survive for long periods in the tract
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Progesterone levels in bitches
Progesterone levels increase near-linearly before ovulation and are predictive of fertility
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Pseudopregnancy in bitches
- Hormone profiles near identical whether pregnant or not
- Nesting, inappetance, abdominal swelling, lactation
- May allow cross-suckling of dominant females' pups
- Ethinyloestradiol + methyteststerone 'sensoral' suppress pituitary lactotrophs (prevent lactation)
- Bromocriptine 'parlodel' is a D-agonist, does have some side effects
- Cabergoline 'gala stop' is a D2 agonist
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Seasonality in queens
- Some seasonality: Jan-Mar, Jul-Sept
- ?Opportunistic, like desert marsupials
- Can start to breed simply if water/ food/ temp improve
- Lower energy demands than bitches and can produce small litters, unlike sows
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Induced ovulation in queens
- Increases chances of fertilisation (solitary species)
- Continual production of waves of follicles
- Some in continuous heat, some show 'cycles'
- Dramatic oestrus behaviour may worry owners- lordosis, rolling, calling, tail deviation
- Coitus --> GnRH release --> LH surge --> ovulation
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Cycles in Jills
- Derived from european polecat
- Non-breeding Jills must be spayed
- Reflex ovulators so continual follicle production --> hyperoestrogenism --> marrow depression-->
>Anaemia
> Clotting disorders
> Immune suppression
> Hair loss tail, then flanks
181
Cycles in the doe (rabbit)
- ALl breeds derived from european rabbit
- Jan-Sept breeding in wild, all year in captivity
- Induced ovulation but often receptive in 2 week 'cycles'
- ? very rare diapause
- Pseudopregnancy if mounted by bucks or other does- nest, hide, fur pluck, aggression
- Pregnancy is about 31 days, can become pregnant almost immediately after giving birth
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Gravid uterus- diagnosis
Palpation:
- Transabdominal in midpregnant carnivores
- Rectal in horses, cattle and pigs
- 'Membrane slip, middle uterine a. fremitus'
Ultrasound:
- Transabdominal, per rectum, vaginal, echocardiography in humans
Radiography is good and reassuring for counting fetuses during birth.
Hormonal: but beware of pseudopregnancy (dogs), prolonged cycles (P), troph tumours hCG
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Gravid uterus- mare
- Foals initially lies with back to the greater curvature of the uterine horn (spine ventrally), with its head towards the cervix
- Early uterine contractions 'roll' the foal so it is spine-to-spine with the mare
- Ventral to guts
184
Gravid uterus- cow
- Usually on the R, in the intestinal recess, displacing intestines dorsally and rumen to the L
- Less often, may extend along R or even L flank
- Calf lies with its back in the greater curvature (spine dorsally) and slightly to the R, with head towards the cervix
- Uterus 'sinks' ventral to gas-filled gut
185
Gravid uterus- size
- Increases volume by 100x in cattle
- Uterus cells hypertrophy rather than proliferate- thins but becomes heavier
- Broad ligament often becomes more muscular
- Ovary is pulled cranioventrally
- Dramatic compression of abdominal and then thoracic organs- cd. VC, lungs etc.
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Birth canal- bony
Pelvic inlet between ilium and pubis.
Diagonal conjugata between ilium and ischium.
Vertical diameter between sacrum and pubis- narrowest stretch domestic animals have to get through.
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Problems with the birth canal in cattle
- Surprisingly narrow
- Sciatic tuberosities protrude into canal
- Symphysis lies more directly below the sacrum, rather than caudal to it
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Birth canal- muscular
- Sacrosciatic ligament (ungulates) + mid gluteal (carnivores)
- Coccygeus (sciatic spine --> T proc Cd2-5)
- Internal obturator
- Levator ani (medial ilium --> haemal arch Cd7)
- Ext. anal sphincter
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Rima vulvae
Bounded by labia minora
Labia majora not prominent (may be present)
Bounded by dorsal and ventral commisures
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Muscles of the vulva and perineum
- Constrictores vulvae et vestibuli
| - Ischiocavernosus everts vulva, esp. mare 'winking'
191
Clitoris
- Lies dorsal to mares rounded commissure
- Penis homologue
- Lies in clitoral fossa (~prepuce), with dorsal frenulum
- Very obvious in horses- site of CEMO?
192
Perineum
- Important in mares, due to the clinical effects of poor conformation
- It is caudal body wall of the pelvic cavity
- Complex of fibrous and muscular tissue around anus and vulva
193
Vulva- ideal conformation
- Labia firm and meet evenly to form a seal
- 2/3 of rima vulvae lie below level of sciatic arch
- Angle between commissures no more than 10 degrees from vertical
194
What can poor conformation of the vulva lead to?
Air retention, urine pooling, faecal soiling
Reduced sperm viability in vagina, endometriosis, placentitis, fetal neonatal sepsis
195
Changes to the birth canal at birth
- Prior to birth relaxin , along with E and P, softens the collagenous structures of the tract, pelvis and perineum
- 'Insinking' over sacrosciatic ligament in cattle, vulval 'swelling'
- Loosening of sacroiliac joint and pelvic symphysis
- During birth the tail is usually raised
196
Which animal completely splits its pelvic symphysis at birth?
Guinea pigs
197
Causes of dystocia (maternal and fetal)
Maternal: Expulsive forces, the canal
Fetal: Oversize, malpresentations
198
Pelvic causes of dystocia
- Immaturity
- Old fractures
- Breed (achondroplasia decreases vertical diameter)
- Other space-occupying lesions
199
Uterine causes of dystocia
- Torsion
- Ventral abdominal rupture (ungulates)
- Ventral deviation (pig) and retroflexion (horse)
- Inguinal hernia
200
Cervical causes of dystocia
- Maybe hormonal
| - Scarring, congenital
201
Bladder causes of dystocia
- Distension
- Eversion (ungulates)- inside out
- Rupture through floor of vagina (ungulates)
202
Vaginal/ vulval causes of dystocia
- Immaturity (any) or hymen (pig)
| - Vulval stenosis (CKCS, Jersey)
203
Dystocia- malposition
- 'Wrong' part of fetus facing maternal spine
- More common in horses due to need for early parturition 'roll'
- 'Normal' for humans
204
Dystocia- malrepresentation
- 'Wrong' part of fetus enters canal
| - Very common and relatively unimportant in polycotous species
205
Dystocia- malposture
All limbs are flexed until parturition, when the fetus takes up the 'driving position':
- Carpal flexion, elbow flexion, shoulder retraction
- Hip flexion, hock flexion
- Lateral deviation of head
206
Why do neonates have little control over their heat loss?
High surface are to volume ratio (larger mammals have better chance of survival)
207
What does a neonates ability to vary heat production depend on?
Endogenous reserves and milk intake
208
Energetically inexpensive ways to defend body temperature from mild cold
- Vasoconstriction
- Piloerection
- Changes in posture to decrease SA
209
Non-shivering thermogenesis
Dependent on brown adipose tissue:
- High metabolic rate
- Rich nerve supply
- Good blood supply
210
Where is brown adipose tissue distributed?
Around the neck, scapula, and thoracic vertebrae and some internal organs
211
Which neonate has no brown fat?
Piglet
212
Evidence for BAT being the major site of sympathetically activated non-shivering thermogenesis
- Temperature within brown fat is greater than temp elsewhere
- Hypoxia and the resultant decrease in blood-oxygen levels supresses heat production by BAT during cold exposure
- In rabbits, excised brown fat from cervical and interscapular regions decreases metabolic response to the cold by 80%
213
Mechanism for activation of BAT (theory)
Related to the uncoupling of substrate use and ATP production in mitochondria, and binding of catecholamines. Injecting adrenaline and noradrenaline has been shown to lead to an increase in heat production by brown fat.
214
Role of type II deiodinase (D2) in BAT thermogenesis
Mediates the full thermogenic response of brown fat to adrenergic stimulation via increased thyroxine (T4) to triiodothyronine (T3) conversion.
215
Maturational effects of glucocorticoids
- Adrenal glands develop capacity to synthesise and secrete adrenaline
- Change the set points of functioning endocrine glands
- Maturational changes of organs
216
Altricial offspring (e.g. rodents)
Rely on pups huddling together in their nest to maintain body temperature.
BAT matures post-natally.
Slow post-natal increase in UCPI correlates with the slowly rising ability to demonstrate non-shivering thermogenesis.
217
Precocial offspring (sheep, cattle)
Able to rapidly switch on non-shivering thermogenesis following cold exposure to the extra-uterine environment.
UCPI is mainly increased immediately prior to birth.
Good defence of body temperature and immediately respond to noradrenaline.
Failure to switch on BAT, e.g. following pre-term birth, impairs heat production and results in hypothermia.
218
Precocial offspring (piglets)
Lacks BAT, as its UCPI gene is non-functional
Entirely dependent on shivering thermogenesis following birth.
A large % of low birth weight piglets die perinatally, compared to piglets of mean or high birthweight.
Muscle glycogen is used primarily for thermogenesis and physical activity, and decreases more significantly than liver glycogen when exposed to cold temperatures.
219
What is the prepartum cortisol surge caused by in most species?
Increased adrenal cortisol output
220
What is the prepartum cortisol surge caused by in the rat and the horse?
Its effects are enhanced by a fall in the level of plasma corticosteroid binding globulin.
221
Impact of stressful intra-uterine conditions on fetal cortisol levels
They become elevated due to HPA axis being activated earlier.
222
What does thyroid hormone activate?
The brown fat around the time of birth.
223
Endocrine and neural regulation
1. Neural:
- Innervation of adrenal medulla
- Cortisol --> increases activity of PNMT --> converts NA to Adr
- Motot maturation
2. Endocrine:
- pituitary-adrenal
- pituitary-thyroid thermoregulation
- insulin/ glucagon
224
Insulin and glucagon around birth
Released in utero, with a large increase at birth.
After birth plasma [glucose] falls as no maternal input.
225
Hypothalamic-pituitary-adrenal axis
Adrenal cortex:
--> Lungs: surfactant production, beta adrenergic receptors
--> Liver: glycogen, gluconeogenic enzymes, IGF gene expression, beta adrenergic and GH receptors
--> Gut: acid secretion, digestive enzymes, mucosal growth
--> Kidney: glomerular filtration rate, tubular Na reabsorption
226
Excretion in newborns
Newborns pass sticky, black fecal matter called meconium (digested amniotic fluid, gastrointestinal secretions and bile)
227
Kidney of newborn
Produced little urea as the animal is synthesising protein.
The collecting ducts of the newborn kidney are sensitive to the actions of antidiuretic hormone.
228
Interuterine growth retardation (IUGR)
Impaired growth and development of the mammalian embryo/ fetus or its organs during pregnancy.
