Reproduction Flashcards
Draw a mature mammary gland and label.
Alveoli
Ducts
Udder cistern
Teat cistern
Which hormones are responsible for mammary gland development?
What process is each responsible for?
- Oestrogen - increased branching and diameter
- Progesterone - alveoli formation
- Prolactin/ GH - speeds up puberty
Mammary glands are modified _________ _________.
Sweat gland
What are the main components of milk? How does colostrum differ?
Milk - water, lactose, protein, fat
Colostrum - Ig, fructose vitamin A, lactose
__ progesterone at parturition causes increased lactose synthesis due to increased ____.
What effect does this have?
Increased
Prolactin receptors.
Increased lactalbumin, the milk protein.
What is the significance of well timed milk let down at parturition?
Too early = leaking out
Too late = starving neonates
What hormone causes contraction of myoepithelial cells and milk ejection?
Oxytocin
The sucking stimulus is vital in maintenance of milk production since it…
Stimulates oxytocin and prolactin release from the pituitary gland and removes FIL
How can puberty be defined?
Male - first ejaculation
Female - maintaining pregnancy without damage/ first cycle
What hormonal changes occur at puberty?
Decreased sensitivity to negative feedback of HPA axis leads to GnRH release in pulses.
Name three factors which cause the onset of puberty.
Age
Fatness - leptin, FA’s and blood glucose
Metabolic status
Seasonality - photoperiod
Social conditions
Name four factors which can increase milk yield.
- Blood supply
- Water intake
- Suckling frequency
- Lactose - glucose (blood)
Draw and label an alveolar cell of the mammary gland
- Fat droplets
- rER/ sER - Fat products
- Golgi apparatus
- Milk - blood barrier - tight junctions
- Milk proteins
6.
What are the major componants of milk?
- Fat
- Protein
- Lactose
- Ions - Na+, K+, Cl-, Ca2+ (free/protein bound)
How does the composition of colostrum differ from that of milk?
How long should milk be witheld from human consumption after parturition?
More fat, protein and vitamin A and reduced lactose.
Immunoglobulins secreted by plasma cells.
4 days.
What are the endocrine controls of lactogenesis during late pregnancy and at parturition?
- Late pregnancy - Increased cortisol, prolactin, oestrogen and placental lactogen.
- Parturition - decreased progesterone - upregulation of prolactin receptors leads a-lactalbumin synthesis (increased milk secretion)
Why is the suckling stimulus vital for galactopoiesis? What processes does it stimulate?
- Pituitary secretion of oxytocin and prolactin
- Prolactin - maintains alveolar cell metabolism and a-lactalbumin secretion
- GH (via IGF-1) does this in ruminants
- Also required are - GH, Insulin, TH and cortisol
- Fedback inhibitor of lactation needs removing
Describe how photoperiod affects cyclicity.
Specifically in the horse and sheep.
Light meets eye - reaches ganglia cells of the eye - travels to the superior cervical ganglion - pineal gland cells - these detect melatonin levels.
Low melatonin has the following effects:
- Horse - long day breeders - kiss neurons stimulated - increased GNRH = cyclicity
- Sheep - short day breeders - kiss neurons inhibited = no cyclicity
The anterior pituitary gland secretes which hormones?
The posterior pituitary secretes which hormones?
- AntPit - FLAT PiG
- PostPit - Oxytocin and vasopressin (ADH)
What happens at puberty in the male to set off the GnRH pulse generator?
Decreased negative feedback sensitivity of testosterone to GnRH leads to LH pulses.
What does GnRH stand for and from where is it released?
Gonadotrophin releasing hormone - secreted by hypothalamus
Meiosis
PMAT - haploid chromasomes produced, genetically different cells, 4 daugter cells
Oogenesis
Primary oocyte - secondary oocyte at LH surge (puberty)
Secondary oocyte - ootid at ovulatio/fertilisation –Zygote
Follicle development
Draw and label a graafian follicle. Which hormones are secreted from which follicular layers?
- Internal layer - granulosa cells convert testosterone to oestrogen in response to FSH
- External layers - theca cells secrete testosterone
Which hormones are dominant in the follicular and luteal phases of the oestrus cycle?
Follicular = oestrogen
Luteal = progesterone
Name and describe the phases of the oestrus cycle.
Proestrus - follicular - luteolysis
Oestrus - follicular - sexually receptive
Metoestrus - luteal
Dioestrus - luteal
Describe the oestrus cycles of:
Cow, ewe, mare and sow.
Describe the difference between short and long loop negative feedback.
The last hormone in a chain of control exerts a negative feedback on the hypophysio-pituitary system = long-loop negative feedback.
Anterior pituitary hormones exert negative feedback effect on hypothalamus = short-loopnegative feedback.
Reflex Ovulator
- In the absence of coitus only have a follicular phase
- Need additional inputs to brain to induce ovulation
- GnRH pulse generator is not sensitive enough to the high oestrogen to induce an LH surge. In these animals there are additional inputs during copulation.
- Stretch inputs from vagina and sensory inputs all combine to increase GnRH.
Corpus Luteum structure and function
Secretes progesterone for the maintenance of pregnancy
Present for about 14 days after follicular phase.
Spermatogenesis
Leydig and sertoli cells are found where? What is their function?
Found in the seminiferous tubules
- Leydig - peripheral - Secrete testerone in response to LH
- Sertoli - central - Secrete inhibin and testosterone (converted to oestradiol and dihydrotestosterone) in response to FSH
What is the function of the sperm-testis barrier?
Tight junctions prevent the haploid cell coming into contact with the adults blood etc since they are considered foreign by the immune system.
How do the cells of the basal and adluminal compartments of the seminiferous tubules differ?
Basal = diploid PGC
Adluminal = haploid spermatocytes ect
What are the vital characteristics of the male endocrine system for sperm production?
- GnRH pulses every 3-6 hours
- Temperature
- LH receptors
- Testosterone in SNT’s
Describe how an erection is formed.
- Increased arterial flow
- Corporal sinusoids dilate
- venous outflow restricted
- Increased intrapenile pressure
- Retractor penis relaxes
Describe the nervous systems input into erection formation.
The PNS uses NANC neurones (NT = NO) which cause the convertion of GTP > cGMP
Once cGTP is metabolised the penis becomes flaccid.
What is the difference between emission and ejactulation?
Emission is the mixing of seminal fluid with sperm.
Ejactulation is the expulsion of fluid and sperm from the penis.
Seminal plasma is secreted by what? What are its main componants?
Secreted by epididymis and accessory glands.
Contains - fructose (energy), hormones and enzymes.
Describe the follicular waves of the oestrus cycle.
Follicular waves are stimulated by FSH, there is often more than one follicular wave since progesterone prevents full development of follicules during the luteal phase of the cycle.
Once luteolysis occurs P4 levels decrease and a dominant follicle develops which is then ovulated at the LH surge.
Why does the length of the epididymis limit a males fertility?
The available store limits the number of fertile breedings within a certain time period.
Sperm need 8-15 days to mature within the epididymis
How does the dominant follicle differ from those in previous stages of the wave?
Dominant follicles have LH receptors
Which hormones cause luteolysis?
Oxytocin causes PGF2a release leading to luteolysis.
What barriers exist to prevent sperm from reaching the ovaries?
- Cervical folds
- Enzymes/ macrophages
- Ejected out
- Retrograde loss
What are the layers covering the testes called? (x7)
Where do each of the spermatic fascial layers arise from?
- Skin
- Tunica Dartos
- Spermatic Fascia
- External - External Abdominal Oblique
- Cremasteric - Internal Abdominal Oblique (+ cremasteric muscle)
- Internal - Transverse Abdominal
- Parietal peritoneum (vaginal tunic)
- Visceral peritoneum
Why are the testis found outside the abdominal cavity?
Which structure helps them get here?
Allows sperm to development (temperature)
The gubernaculum aids the descent of the testes into the scrotum through the inguinal canal.
Inguinal Canal
Structure (x2) and development (M/F)
Clinical Significance. What are the common structures involved here? (x4)
A potential space between abdominal wall muscles.
- Deep Ring = IAO
- Superficial Ring = EAO
Formation : Outpouch of peritoneum (vaginal process) pushes through IC. Males into the scrotum. Females (bitch) rudimentary vaginal process extends to IC.
Clinical Significance: Formation of inguinal hernias (most common in rabbit and pig. Most commonly Small intestine, Greater omentum, Bladder, Uterus
Which layers of the testes are incised in an open compared with closed castration?
How do the two procedures empirically differ?
Open: Skin, TD, spermatic fascia and parietal peritoneum (VT) = 6
Closed: Skin and external spermatic fascia = 3
In the open castration the surgeon enters the peritoneal cavity.
What type of penis do each of the domestic species have?
(ie musculocavernous vs fibroelastic)
What is mean by each of these definitions?
- Musculocavernous - Contains lots of smooth muscle, increase in length and diameter during erection - Horse, carnivore
- Fibroelastic - Contains lots of fibrous material, not much expansion occurs during erection, has a sigmoid flexure - Bull, ram, boar
How does erection in the musculocavernous penis and the fibroelastic penis differ?
Musculocavernous relies upon blood engorement entirely whereas a fibroelastic penis also relies upon relaxation of the retractor penis muscle to allow straightening of the sigmoid flexure.
How does the glans penis differ in each of the domestic species?
- Bull – slightly spiralled
- Boar – corkscrew shaped with a left hand thread
- Ram – Vermiform appendage, extension of urethra
- Stallion – Mushroom shaped, slight protrusion of the urethra
- Dog – substantial, divided into the bulbus glandis proximally and pars longa glandis distally
- Tom cat – cone shaped with Keratinised Papillae, directed caudally
Describe the prepuce.
Tubular cutaneous sheath covering free part of non-erect penis
Preputial cavity with:
- External lamina = normal skin
- Internal lamina = thin hairless squamous epithelia
Contains muscles that keep preputial orifice closed and retract prepuce
Name and describe the accessory glands of the male reproductive system.
(x4)
What is the function of these glands?
The accessory glands secrete seminal fluid
- Not all glands present in all species
- Ampulla of ductus deferens
- In dog this is largely covered by the prostate
- Vesicular gland
- Absent in carnivores
- Prostate gland
- Lies dorsally on neck of bladder
- Has disseminate parts
- Bulbo-urethral gland
- Empties into distal part of pelvic urethra
- Absent in dogs
How does erection in the dog differ to that of other domestic species?
In dog intromission easily achieved due to os penis and then full erection occurs by expansion of bulbus glandis and extension of pars longa glandis AFTER intromission
Describe the penis of the dog.
- Corpus cavernosum penis
- Left and right separated
- Cranial part ossified, os penis, ventral groove that contains corpus spongiosum / urethra
- Corpus spongiosum penis
- Bulb of penis, exceptionally large
- Glans penis is double structure
- Bulbus glandis coves proximal half of os penis
- Pars longa glandis covers distal half of os penis
What are the three muscles of the penis called?
Describe their anatomy and action.
- Retractor penis muscle
- Slender muscle connected to internal / external anal sphincters and coccygeus
- Passes ventral to penis in midline, attach 1/2 along length
- Mainly smooth muscle - retract penis into sheath
- Ischiocavernosus muscle
- Covers crura
- Origin - ischiatic arch, insertion - tunica albuginea of cc
- Prevents venous drainage during erection
- Rhythmic contractions ^ pressure in cc during erection
- Bulbospongiosus muslce
- Thick midline circular muscle overlying caudal enlargement of cs
- Prevents venous drainage of blood during erection
- Rhythmic contractions ^ pressure in cc during erection
By which vessels is blood supplied and drained from the reproductive system of the male?
- Arterial
- Internal pudendal artery
- Curves around ischiatic arch - branches deep into erectile tissue at root of penis
- Continues along dorsal surface of penis outside tunica albuginea (= dorsal artery of penis)
- Venous
- drained at root of penis via internal pudendal vein
- Horse - also body of penis into external pudendal vein
What are the three main branches of the internal pudendal artery of the male and which structures do they supply?
- Artery of the bulb – supplies the corpus spongiosus
- Deep artery of the penis – supplies the corpus cavernosum
- Dorsal artery of the penis – supplies the glans penis
Which structures are held within the spermatic cord?
Describe the vessels.
What is the significance of the venous structure surrounding artery?
- Spermatic cord - encases structure in a peritoneal fold (= mesorchium) continuous with vaginal tunic
- Ductus deferens & testicular vein / artery in
- Testicular artery conveys blood direct to testis. Becomes tortuous close to testis
- Testicular vein (mesh) encasing testicular artery (= pampiniform plexus) allows cooling of arterial blood to testis via heat exchange with venous blood
Which end of the epididymis emptys into the ductus deferens?
Tail
Which structure attaches the spematic sac to the scrotum?
Scrotal ligament
Describe the peritoneal attachments of the ovaries.
(x4)
- Mesovarium (ovarian ligament)
- To lateral body wall at caudal pole of kidney
- Contains ovarian artery & vein
- Must be ligated in a spay
- Continuous with mesometrium
- Mesosalpinx
- To uterine tube
- Suspensory ligament
- To lateral body wall at caudal pole of kidney
- Very short in bitch and must be broken to allow exteriorisation of ovary for a bitch spay
- Proper ligament of ovary
- Ovary to cranial end of uterine horn
How is the ovarian bursa formed?
- Pocket of peritoneum that encases ovary
- In bitch it contains a lot of fat that obscures it complicating the spay procedure
- Bounded by:
- Proper ligament of ovary medially
- Mesosalpinx laterally
- Mesovarium cranially
- Uterine horn caudally
What is the overall shape of the uterus of the dog? (x2 parts)
Which ligaments attaches it to the body wall? (x1 containing another)
Where does the uterus lead to
- Uterine horns attach to ovaries cranially and body of uterus caudally in a “Y-shape”
- Attached to lateral body wall by mesometrium (broad ligament)
- Round ligament of uterus runs in broad ligament from ovary through inguinal canal (= foetal remnant of gubernaculum)
- Body of uterus continues into cervix
What occurs hormonally to promote lactogenesis and galactopoiesis?
Lactogenesis - >cortisol, prolactin and E2, <p4></p4>
<p>Galactopoiesis - Prolactin, IGF1 - GH, Insulin, TH, cortisol, feedback inhibitor of lactation</p>
</p4>
Name a prolactin inhibitor and its action.
ADME
Contraindications and Adverse effects.
Cabergoline - galactostasis and luteolysis.
It is used in oestrus, promote abortion and treat false pregnancy.
A-GI tract, D-Albumin bound, M-Liver, E-Kidney, T1/2 20hrs
Contraindications - pregnancy
Adverse Effects - Vommiting, drowsiness, transient hypotension
Describe the pharmacological data of synthetic Oxytocin.
What is it used for?
Adverse effects?
A - IM/IV, M - Liver, E - Kidney
T1/2 - 1-6 minutes (IV), persists if given IM
Used to promote myometrial contraction and milk ejection, adverse effects include uterine dystocia.
What two types of receptors are used by sex steroids?
Membrane (decrease myometrial contraction) and nuclear (mucus secretion)
Describe the ADME data for sex steroids.
D - Lipophilic and protein bound
M - Hepatic - glucoronide and sulphate conjugates
E - Urine and bile
Name three endogenous androgens
Testosterone, dihydrotestosterone and androstenedione
What are the physiological effects of androgens?
- Masculinising effects
- Secondary sex characteristics
- Spermatogenesis & >libido
- Anabolic effects
- >protein synthesis partic skeletal muscle
- >growth bone & cartilage
- High doses inhibit gonadotrophins & will suppress oestrus cycle
- >erythropoiesis
What two pharmacological preparations are available for androgens?
Describe their pharmacological properties.
- Testosterone
- 1/2 life = 8d - action 2-4wks
- Danazol - used in immune-mediated disease
- Nandrolone - weak androgen (cats with chronic renal failure)
Describe the action & pharmacology of Nandrolone.
- Anabolic steroid ( weak androgen)
- > appetite, erythropoiesis, protein synthesis
- Used to treat cats with chronic renal failure
- T½ (6d - inj every 3 weeks)
What are the adverse effects of androgens?
- Infertility or oligospermia
- Perianal adenomas perineal hernias, prostatic disorders & behavioural changes
- Masculinisation of females
- hepatotoxicity
Name two androgen-inhibitors and how they act.
- Finasteride
- 5 – alpha – reductase inhibitor
- Inhibits formation of dihydrotestosterone (Metabolite of testosterone)
- 5 – alpha – reductase inhibitor
- Osaterone ( competitively prevents binding of androgens to prostatic receptors)
- Steroid chemically related to progesterone. It is a potent Progestogens and a potent anti-androgen and has glucocorticoid effects.
What can oestrogens be used to treat?
Oestriol - treat urethral sphincter incompetence in spayed bitches (x for intact)
What are the physiological effects of progestogens?
- > glandular growth mammary gland after priming with oestrogens
- Prolong the luteal phase of the oestrus cycle
- Desensitise the myometrium to oxytocin
- Anabolic effects
- –probably due to > appetite & < activity
What are the adverse effects of progestogens
- Endometrial hyperplasia, endometritis & pyometria
- Glucocorticoid activity may induce diabetes mellitus
- Inhibition of ACTH
- Behaviour changes
Why should endogenous progesterone NOT be given orally?
It is rapidly inactivated in the liver
Regumate & 1/2 life?
Altrenogest
Short half life of 10hrs
A chemical castration and its pharmacological data.
Delmadinone
- Inhibits FSH & LH < testosterone
- Long T½ around 8d
- Cortisol response to ACTH is diminished after a single treatment
A synthetic progestogen used for oestrus supression and false pregnancy in cats, dogs and ferrets.
Proligestone (less side effects than progestogens)
This progesterone receptor blocker is used to promote abortion, treat pyometra and induce parturition.
Aglepristone
What are the main proteins present in milk?
Caseins (80%)
Whey proteins - lactalbumin (alpha and beta)
How is pregnancy recognised in each of these species?
- Horse
- Pig
- Sheep/cow
- Bitch
- Horse - conceptus migrates around the uterus secreting maternal recognition of pregnancy proteins which inhibit PGF2a release
- Pig - Oxytocin is released exogenously, they need 2+ conceptus to work
- Sheep/cow - blastocyst releases interferon which blocks oxytocin receptor production
- Bitch - no luteolysis
What is the purpose of capacitation?
Describe the process.
How does this reaction lead to fertilisation?
Full maturation of sperm when sperm reaches the female reproductive tract.
ZP3 receptors are revealed which allow the sperm to bind to oocyte.
What reactions occur once the sperm reaches the ovum in the female reproductive tract?
- Zona Block - ovum releases cortical granules which prevent polyspermy
- Acrosomal reaction - removes the sperms outer membrane - full binding
Why are repeat breedings vital in the horse?
Explain
Window of fertilisation is short.
- Ovulation occurs on d5 of oestrus
- Ovum are viable for 6-8hrs after this
- Sperm are viable for 4-5 days
- If horse is mated at the beginning of oestrus sperm will not be viable when the egg is released
Describe the window of fertilisation of the cow and bitch.
- Cow - ovum released 24-32hrs after the onset oestrus (~4hrs after oestrus ends). Sperm are valid for 48hrs is repro tract of female
- Bitch - Ovulation occurs 2-3d after oestrus onset and egg is viable for 4-5d (BUT only fertilisable at d2 after release. Sperm are valid for seven days.
Match these species to their type of placenta.
- Horse
- Cow
- Sheep
- Cat/ dog
Describe each placenta type.
- Horse - Diffuse - Microcotyledons
- Cow - Cotyledonary (concave) - lots of points of attachment
- Sheep - Cotyledonary (convex)
- Cat/dog - Zonary - band of chorionic villi, individual for each foetus
Draw and name the features of a cotyledonary placenta.
- Cotyledon: the fetal side of the placenta
- Caruncle: the maternal side of the placenta
- Placentome: a cotyledon and caruncle together
How many layers do epitheliochorial and endotheliochorial placentas have?
Name & draw the layers.
- Epi - 6
- Endo - 5
Chorionic capillary, chorionic interstitium, chorionic epithelium, endometrial epithelium, endometrial interstitium, endometrial capillary.
In bold is the layer NOT present in endo.
What are the four foetal membranes and what are they made up of?
Identify which of the layers contributes the placenta.
- Amnion - surrounds amniotic cavity - trophectoderm + mesoderm
- Chorion - trophectoderm + mesoderm
- Allantochorion - chorion + allantois
- Yolk sac membrane - surrounds yolk sac - endodermal
What is the difference between primate and non-primate implantation?
Primates implant, non-primates attach
How does the Y chromosome stimulate sexual specificity of the male?
- SRY gene
- Antimullerian hormone
- Paranephric duct degenerates
- Leydig cells differenciate
- Testosterone - Duct system
- Dihydroestrogen - Penis, scrotum and glands
How long does the corpus luteum persist during pregnancy in each of these species?
- Cow
- Pig, bitch, queen
- Horse
- Sheep
What is the function of the CL in pregnancy?
- C - 6-8m/9m
- PBQ - Entire pregnancy
- H - 70d/11m
- S - 50d/5m
Produces progesterone which mainains pregnancy. After CL regresses the placenta produces P4. (NOT in horse)
Endometrial cups are unique to which of the core species?
What is their function? How long do they persist and what happens after this?
Horse
Found around the endometrial cups they produce eCG (secretion of luteotrophin) which causes the formation of accessory CLs & helps maintain the primary CL.
They persist up to around d100 at which time the placenta takes over.
Binuclear giant cells
Function.
They form ~20% of the ruminant placenta and allow the transfer of complex molecules from foetus to mother, eg placental lactogen, protein B.
Function not completely known.
Outline fergusons reflex.
What other neuroendocrine reflex is present at parturition?
- Cervical stretch cells in uterus detect stretch due to foetal presence.
- Spinal cord - Hypothalamus - Post pituitary
- Oxytocin released
- Augments uterine contraction
Spinal reflex which causes abdominal straining.
What feed back mechanism is instigated in response to cervical stretch at parturition?
Positive
- Oxytocin release
- PGF2a
- Uterine contraction
- Cervical stretch
- Continues until the end of stage 2 when the foetus is expelled from the uterus
Parturition stage 3
How does it vary with species?
Villi regress and become less rigid = expulsion of foetal membranes.
Timing
- Bitch - with each neonate
- Cow - 30m-12hrs
- Mare - 30-90m
- Sheep - 5-8hrs
- Sow - 1-4hrs
Foal heat
Mare resumes cyclicity 7-10d after parturition, the uterus may not be fully involuted but compensation comes as pregnancy can occur in the contralateral uterine horn.
How does lactation affect cyclicity in the sow?
How is this tackled?
Lactation inhibits cyclicity in the sow, therefore piglets are often weaned at 3-4 weeks.
How long do each of the core species take to resume cyclicity after parturition?
- Carn - anoestrus
- Cat 30d
- Dog 150d
- Mare - 7-10d / anoestrus @winter
- Sheep - 150d (anoestrus since short day breeders)
- Cow
- Beef - 50-60d - due to lactation
- Dairy - 18-25d
Describe the series of events leading to parturition.
- Uterine crowding/ placenta can’t support = foetal stress
- Foetal ACTH > cortisol > PGF2a
- Luteolysis - reduces progesterone
- Relaxin = pelvic ligaments stretch
- Placental P4 > Oestradiol
- Lubricants secreted
- Myometrial contraction
How does induction of pregnancy in the mare differ from other species?
Foetal gonads produce ample testosterone and oestrogen = lots of oxytocin receptors. (responsive to oxytocin for induction)
