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40 Cards in this Set

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RESPIRATORY SYSTEM

DEVELOPMENT

5 DEVELOPMENTS

2 KEY WORDS
Respiratory Diverticulum
- forms as outpouching of ventral aspect of foregut

Esophagotracheal Septum
- separates respiratory system from GI system

Elongation

Branching
- produces bronchi and bronchioles
- branching can occur post natally

Respiratory Movements
- required in utero to aid development of musculature associated with respiration

Precocial species have highest amount of in utero lung development
RESPIRATORY SYSTEM

ABNORMAL DEVELOPMENT

NAME TWO
Esophagotracheal Fistula

Hypoplasia
ESOPHAGOTRACHEAL FISTULA
Incomplete speration of respiratory and digestive tract

Results from incomplete development of Esophagotracheal Septum

Rare
- can occur in any species
- usually aquired vs congenital
- mainly foreign body ingestion

Presentation
- aspiration pneumonia
- bloating
RESPIRATORY TRACT HYPOPLASIA
Can occur in any portion of respiratory tract

Tracheal
- common in brachycephalic breeds

Lung Hypoplasis
- absence of lobe or portion of lobe
- usually related to OTHER abnormalities that decrease size of thorax cavity
~~~ ie congenital diaphragmatic hernia
DIGESTIVE SYSTEM

DEVELOPMENT
Develops as Tube
- suspended from dorsal and ventral mesentaries which are continuous
- mesentary caudal to diaphragm
- mediastinum cranial to diagphragm

Ventral Mesentary
- exists fully for short period
- Ventral Mesogastrium
~~~~ important for development of lessor omentum
- Caudal Mesentary
~~~~ contributes to median ligament of bladder
- necrosis and apoptosis ablate majority of ventral mesentary

Foregut
- Pharynx
- Esophagus
- Stomach
- Liver
- Pancreas
- Cranial Duodenum

Midgut
- remaining SI
- cecum
- ascending colon
- portion of transverse colon

Hindgut
- remainder of transverse colon
- descending colon
- cloaca
~~~~ rectum
~~~~ anal canal
- also contributes to urethra
SIMPLE STOMACH

DEVELOPMENT
Starts as Tube

ASYMETRICAL growth DORSALLY
- greater growth on dorsal aspect vs ventral aspect
~~~~ greates distention
~~~~ promotes curvature

ROTATION
- results from asymetrical growth
- greater curvature of stomach becomes ventrally positioned
COMPLEX STOMACH

DEVELOPMENT
ASYMETRICAL DORSAL GROWTH and ROTATION
- initially same as simple

Expansion of Greater Curvature
- forms Rumen
~~~~ Dorsal Sac
~~~~ Ventral Sac

Expansion of Lessor Curvature
- forms Omasum

Pocket develops near Rumen
- forms Reticulum

Remainder of stomach
- forms Abomasum
- majority of stomach in neonate
- nursing tf high protein diet does not require fermentation
- abnormal development of muscular groove that facilitates movement of fluids from cardia to abomasum results in
~~~~ bloating
~~~~ maldigestion
~~~~ stunted growth
COMPLEX STOMACH

DEVELOPMENT

MIGRATION
Ventral Sac of Rumen initiates movement
- inverts caudal-dorsally
- migrates to definitve left dorsal position

Movement of Rumen forces Reticulum to move cranioventrally

Omasum and Abomasum move to right
ROTATION OF GUT

AROUND

CRANIAL MESENTERIC ARTERY
Yolk Sac
- aids rotation
- is cranial to majority of development
- provides attachment along with Cranial Mesenteric Artery
- tf as gut elongates it rotates around Cranial Mesenteric Artery
~~~~ viewed dorsally rotation is clockwise

Development and Rotation take place outside of abdominal cavity
- via Physiological Umbilical Hernia

Development and Rotation is species dependent
- Carnivores simple little twisting
- Herbivores complex hindgut high amount of twisting
MECKEL'S DIVERTICULUM
Remenant of Yolk Sac

Failure to Detach
- results in abnormalities
- diverticulum in Jejunum
- Fistula between umblilicus and small intestine
~~~~ leakage of intestinal contents
~~~~ traps organs and intestines
- sttachements
~~~~ trap organs and intestines
INTESTINAL ATRESIA
ATRESIA
- occulsion of lumen

Mechanisms
- As GIT develops there is a large amount of proliferation
~~ internal proliferation can occlude lumen if relative rate exceeds elongation rate
~~ exacerbated by
~~~~ folds withing lumen
~~~~ lack of breakdown of cells withing lumen
- Lack of blood Flow to specific portion of GIT
~~ low proliferation and elongation create oclusion
- Lack of Regresion of Yolk Sac
- Physical trauma
~~ ie Iatrogenic during palpation 1st trimester
~~~~ grapefruit size in cows

Occurance
- can be autosomal ressesive
- Sheep most common
- Cattle
- Pigs
- Dogs
- Horses

Presentation
- Initally normal appetite
- expansion of intestines and bloating
- extreme pain
- die within a few days
INTESTINAL ATRESIA

5 TYPES
Oral end swells due to ingestion of amniotic fluid and accumulation of muconeum

Mucosal Web
- thin membrane completely seperates proximal and distal ends

Fibrous Cord
- cord completely seperates proximal and distal ends

Mesenteric Gap Defect
- complete seperation of proximal and distal intestine

Apple Core Type Deformity
- long isolated segment of intestine coils upon itself

Multiple Areas
- several areas of mesenteric gap
ATRESIA ANI

NORMAL DEVELOPMENT
Normal Development

Common Cloaca contains
- exit from bladder
- exit from hindgut
- passage to alantois

URORECTAL SEPTUM
- develops in mammals
- seperates urogenital and GI systems
- Partitions cloaca

CLOACAL MEMBRANE
- prevents urinary of GI contents from entering Amnionic Fluid
- eventually is divided by migration of Urorectal Septum to become
- UROGENTITAL MEMBRANE
- ANAL MEMBRANE
ATRESIA ANI

ABNORMAL DEVELOPMENT
No Anus

Low Atresi Ani
- lack of regression of Anal Membrane
- usually easy to fix

High Atresi Ani
- lack of development of Anal Rectal Canal
- may or may not involve lack of Anal Membrane Regression
- usually have formed anus
- involves rectal muscles
- failure of cells to degenerate
~~ tf lumen ocluded
- may or may not have anal sphincter
- poor prognosis
FISTULAS

NAME 3 OF THE FAR END
Urethral Rectal Fistula
Recto Vaginal Fistula
Urethro Vaginal Fistula

Result from
- Failure of Urorectal Septum to migrate
~~ abnormalities of Cloaca
~~ interuption of migration
~~ tf temporary loss of blood supply
- Premature Rupture of Cloacal Membrane
~~ tf no place for UroRectal Membrane to fuse

Presentation
- Urinary Infection
- Passing urine through Rectum
- Feces trapped or passed through Urethra
- Urine Scalding
OVERO LETHAL WHITE SYNDROME

COURTESY OF JOE
aka
- Congenital Ileocolic Agangliosis
- Congenital Aganlionic Megacolin

Overo
- selected for by desire for specific white spotting pattern
- pigmented dorsal midline
- ventral white spotting laterally and ventral
- HOMOZYGOUS DOMINANT IS LETHAL
~~ EDNRB gene

Affected foals are completely white with blue irises
- note not all foals of this phenotype are Homozygous for EDNRB

Failure of NEURAL CREST CELL MIGRATION to Intestines
- mainly colon
- also ileum
- results in absence of GANGLIA which are important for PARASTOLSIS
- tf normal parstolsis in upper GI and absence in lower
- tf build up of muconeum in lower GI enlarges colon
- may also involve Atresia Ani or other Intesitinal (usually lower) Atresia

Presentation
- extreme pain
- colic signs

Occurence
- mainly Paint Horses
- other horse breeds
- humans
- rodents
- similar syndrome in dogs

Can be tested for in advance of breeding
URINARY SYSTEM

GENERAL DEVELOPMENT
Intermediate Mesoderm
- Forms Urinary and Genital Systems
- proliferates to form UROGENITAL RIDGE

Urogenital Ridge
- internally forms NEPHROGENIC CORD
~~ forms Kidney and Ureters
- externally forms GONADORIDGE
~~ forms Gonads

Note
- kidneys function in fetus
- not required because Dam extracts waste from allontioc fluid
~~ tf fetus can survive to term without kideys
- kidneys ARE required for proper development of genetalia
KIDNEY DEVEOPMENT

PRONEPHROS
Develops most crainialy
- 7 to 8 primative tubules
- tubules fuse to form PRONEPHRIC DUCT

Pronephric duct grows caudally to terminat in Cloaca

Not functional in veterinary species
- except sheep
- degenerates shortly after development
~~ leaves pronephric duct behind
~~~~ becomes MESONEPHRIC DUCT
KIDNEY DEVEOPMENT

MESOONEPHROS
Develops as Pronephros degenerates

Functional
- 70 to 80 tubules
- drains into MESONEPHRIC DUCT which drains into Cloaca

Simialr Development to true Kidney
- has Glomerulus and Loop in excretatory tubule
- loop is NOT loop of Henle

Degenerates
- except for a few caudal tubules

Mesonephric Duct
- persists in males
~~ important for reproductive system
- degenerates in females
KIDNEY DEVEOPMENT

METANEPHROS

HOW MANY PARTS

NAME THEM
Forms Adult Kidney
- initially lobulated
- subsequent fusion in applicable species

URETERIC BUD
- grows out of Mesonephric Bud
- contributes to
~~ Ureter
~~ Renal Pelvis
~~ Collecting Ducts

METANEPHROGENIC BLASTEMA
- caudal region of Nephrogenic Cord
- forms Nephrons

Ureteric Bud imposes on Nephrogenic Cord
- Nephrogenic cord is then induced to become Metanephrogenic Blastema
- Metanephrogenic Blastema then induces Ureteric Bud to elongate and form
~~ Renal Pelvis
~~ Collecting Ducts
- Renal Pelvis and Collecting Ducts induce Metanephrogenic Blastema to produce
~~ Nephrons
KIDNEY

MIGRATION
Development of Metanephros occurs in close proximity to Cloaca and Rectum

Reproductive System development occurs at the same time

Kidney migrates cranially at same time as Gonads migrate caudally
- tf cross over of Mesonephric Duct and Ureters
BLADDER

DEVELOPMENT
Bladder Develops as Expansion of Uracus

Urorectal Septum divides Bladder from GIT
- forms UROGENITAL SINUS

Entrance of Ureters into Bladder
- occurs in TRIGONE REGION
URETERS

ECTOPIC
Ureters DO NOT enter Trigone region of Bladder
- usually enter neck of bladder
- also urethra
- 75% unilateral
~~ may be asymptomatic
- 25% bilateral
~~ always clinical signs

Abnormal Development
- usually result of abnormal development of Urogentital Sinus
- also disruption of meso or meta nephric ducts
~~ tf ureter in urethra
~~ or Vas Defrens and Seminal Vesicles
- also crossover of of Mesonephric Duct and Ureters
- results in urine drainage into Vas Defrens and Seminal Vesicles

Presentation
- leaking
- may have hypoplastic bladder
- retrograde passage of urine
~~ tf urinary tract infections

Occurance
- Genetic Association
- Most common in dogs
- presentation at 3 - 6 months
- symptoms vary depending on placement
- Females 8x more likely than males

In females may also get abnormal development of PARAMESONEPHRIC DUCT
- ureters enter
~~ vagina
~~ uterus
- vaginal or uterine infections
URETERS

HYDRO
Ureters enter and travel a distance in mucosa of bladder

Constricions of Flow cause a Backlog of urine in Ureter
- enlarged ureters
- enlargement of renal pelvis
- impinges on kidney
~~ tf non functional kidney
URACUS

PATENT
aka Persistent

Urachus connects umbilical cord to Bladder
- umbilical cord excretes into allantois

Normal Development
- stretching during rupture of umbilcal cord stimulates urachus to close

Abnormal Development
- Failure of urachus to close
- Umbilical Torsion
~~ causes back flow and enlargement
~~ tf stretch/rupture insufficient to close
- Iatrogenic
~~ cut umbilical cord to close to abdomen
~~ tf insufficent space for development of necrotic tissue in urachus
- Aquired
~~ Naval Ill aka Omphalophlebitis
~~ urachus becomes infected
~~ tf opens from inflammation

Presentation
- urine from urachus
URACHUS

PATENT

INTERNAL
Urachus closes extenally but open internally

Iatrogenic
- cut to close

Presentation similar to ruptured bladder
~~ Enlarged Abdomen
~~ Depression
~~ Urine in Abdomen
REPRODUCTIVE SYSTEM

DEVELOPMENT

HOW DOES IT START
With great INDIFFERENCE

Complex hormonal interactions determine sex
- ie if you say testosterone she will cut your head off see previous material

It all starts with GERM cells in the Yolk Sac
- migrate via GIT to GENITAL RIDGE
~~ during mesonephric stage when Genital Ridge bulges into coelum
- take up residence forming primative sex cords
- eventually form sperm or ova

Primative Cords
- in males form semineferous tubules
~~ incomplete at partuition
~~ complete development at sexual maturity
- in females form supporting cells for ova
~~ germ cell and folicle proliferation complete (just for this course) by partuition
REPRODUCTIVE SYSTEM

DEVELOPMENT

DANCE OF THE DUCTS
MESONEPHRIC DUCT
- Male Reproductive System
~~ Edididimus
~~ Ductus Deferens
~~ Penile and Pelvic Urethra
- Female Reproductive System
~~ degenerates leaving hole which becomes supporting structure for reproductive tract
~~~~ Mesovarium
~~~~ Salpinx
~~~~ Mesometrium

PARAMESONEPHRIC DUCTS
- condense out of Mesochyme
- Male Reproductive System
~~ degenerates
~~~~ sometimes leaves a tiny little uterus
~~~~~~ maybe Hershel will get lucky
- Female Reproductive System
~~ migrate together and fuse forming Uterus
~~ degree of fusion is species dependent
~~ degree of fusion is proportional to size of Body of Uterus
~~ region that does not fuse forms horns of uterus
~~ fusion produces
~~~~ Cervix
~~~~ Cranial 1/3 of Vagina
~~~~ Rabbits have little fusion
~~~~~~ tf double cervix
VAGINA

DEVELOPMENT
Caudal 2/3 develops from VAGINAL PLATE region of UROGENITAL SINUS

Vaginal Plate grows towards cranial 1/3 of vagina
- lumen forms when Vaginal Plate reaches cranial vagina
- vaginal plate regresses at Wall of Urogenital Sinus
- remenant of Vaginal Plate froms
- Hymen
DOUBLE VAGINA
Incomplete migration and fusion of Paramesonephric Ducts
GUBERNACULUM

DEVELOPMENT

REMEMBER SHE THINKS THIS ONE IS NEAT
Condensation of mesenchyme within INGUINAL FOLD

Testosterone and other Gonadotropins cause swelling of Gubernaculum
- enlarges Inguinal Canal

Later in male development
- Scrotal Swellings develop
- gubernaculum dehydrates
~~ creates space in inguinal canal
~~ tf allows passive movement of Testis into Inquinal Canal
- but Testis are TOO LARGE to pass

Increase in Abdominal Pressure
- required to pass testis through Inquinal Canal
- usually supplied during partition
~~ this is the "neat" part
- testis can also be pushed into scrotum post partuition via coughing etc
- some species move testis in and out of inguinal canal through out life
- ie Rodents
- Sumo Wrestlers
~~ according to Stu
CRYPTOCHIDISM
Testis Retained in Abdominal Cavity
- absence of testosterone
- low levels of signalling receptors

Genetic Associations
GENITALIA

EXTERNAL

HOW MANY SWELLINGS
Genitital Tubercle
- Saggital Plane
- Male
~~ Elongation to form Phallus
- Female
~~ Regression to form Clitoris
- Urethra
~~ ventral Urethral Fissure
~~ remains open in early development
~~ closes ventrally in later development to form Urethra
~~~~ ie during phallic elongation stage

Genital (aka Labial) Swellings
- bilaterally adjacent to Genital Tubercle
- Male
~~ Scrotum
- Female
~~ Labia

Urogentital Folds
- Bilateral
- lateral to Genital Swellings
HYPOSPADIA
Incomplete closure of Urethral Fissure

Genetic Associations
- note less extreme malformations capable of reproduction
HERMAPHRODITISM

TYPES
INTERSEX
- having both male and female genetalia

TRUE HERMAPHRODITE
- both male and female genetalia
- Presence of BOTH male and female Gonads
~~ via presence of ovatestis
~~~~ ie ovarian and testicular tissue in one structure
~~ or via presence of both ovaries and testis

PSEUDOHERMAPHRODITE
- Chromaosomal and Gonadal Sex in Agreement
- External or Internal Genitalia are Ambiguous
~~ ie one or more structures of NON-Chromosomal sex
HERMAPHRODITISM

MECHANISAM
Androgen Insensitiviy

Defect of Androgen Receptor Gene on X chromosome

Receptors
- do not bind Androgens
- or binds but does not function properly

Results in Varying Degrees of FEMINIZATION
TESTICULAR FEMINIZATION
Animals that are XY Chromosomally

Testosterone Production and Conversion to Dihydrotestosterone are Normal

Androgen Receptor gene on X chromosome defective
- tf Androgen Receptors do not bind or do not function properly

Results in Lack of Androgen Dependent Masculinization
- tf animals have
~~ External Female Secondary Sex Characteristics
~~ No Uterus
~~ Internal Testis that lack Epididymis
~~~~ Note main structure of Testis due to SRY gene
~~ No male structures that dervive from Paramesonephric Duct
~~~~ Vas Deferens
~~~~ Epididymis

Presentation
- infertile
- failure to cycle
- stallion like behaviour
INTERSEX

POLLED GOATS
Polled is Dominant Trait
- pp horned
- Pp polled and fertile

PP
- Male
~~ polled
~~ intersex
~~ 50% are infertile
- Female
~~ polled
~~ intersex
~~ 100% infertile
SEGEMTAL APLASIA OF PARAMESONEPHRIC DUCT
aka White Heifer Disease
- mismonmer
~~ originally observered in Herford Short Horns
~~ Rr Roan
~~ RR White with high incidence of Segmental Aplasia
- Mainly Cattle
- also Horses, Cats, Dogs, Pigs, Sheep and Camelids

Abnomality of Female Reproductive Tract
- arrest during development of Paramesonephric Duct
~~ via disruption of blood supply during development
- tf segmented development of any or multiple sections of reproductive tract
- defects
~~ Vagina
~~ Cervix
~~ Uterus
~~ Uterine Tubes
- OVARIES ARE NORMAL

ABSENT HORN
- one side of Paramesonephric Duct failed to develop normally
- low fertility but may breed normally

DOUBLE CERVIX
- Incomplete Fusion of Paramesonephric Ducts
- Fertile
- High incidence of Dystocia
- Cervix susceptable to tearing

APLASIA OF LOWER HORN
- Segment of Paramesonephric Duct did not develop normally
- remainder of Paramesonephric Duct did
- Upper portion of Horn SWOLLEN
~~ fluid produced by uterus cannot drain through APLASTIC SEGEMENT to
vagina
- decreased fertility
SEGMENTAL APLASIA OF PARMESONEPHRIC DUCT

3 PRESENTATIONS
ABSENT HORN
- one side of Paramesonephric Duct failed to develop normally
- low fertility but may breed normally

DOUBLE CERVIX
- Incomplete Fusion of Paramesonephric Ducts
- Fertile
- High incidence of Dystocia
- Cervix susceptable to tearing

APLASIA OF LOWER HORN
- Segment of Paramesonephric Duct did not develop normally
- remainder of Paramesonephric Duct did
- Upper portion of Horn SWOLLEN
~~ fluid produced by uterus cannot drain through APLASTIC SEGEMENT to
vagina
- decreased fertility