Embryology Flashcards
1
Q
Environmental causes of congenital (birth) defects
A
drug (antibiotics, pain meds, vaccinations, topical medicines), plant, infection (viral, protozoan, or mycotic), pesticide, radiation
Anything that mother come in contact with
2
Q
presentation of birth defects
A
can present immediately or will not cause any noticeable signs
Some defects cause abortions
3
Q
critical period
A
time when organ or organ system is developing
cells are replicating
4
Q
veratrum californicum
A
false hellebore, corn lily, ingested on day 14 can cause severe defects. cycloptic lamb
5
Q
Cerebellar hypoplasia
A
underdeveloped cerebellum
Genetic, infectious and toxic
Bovine Viral Diarrhea (BVD) impacting gestation between 100-170 days.
Feline panleukopenia during las 10-14 days of gestation to 10-14 days postnatal
6
Q
cell restriction
A
increases with differentiation.
Totipotent is least restrictive and non-mitotic functional cells are most restrictive
7
Q
totipotent
A
zygote can give rise to whole animal
8
Q
Factors surrounding cell
A
impact gene expression as well as cell contact
9
Q
Which stage is first occurence of restriction?
A
Morula stage
10
Q
fates of blastomeres?
A
outer blastomeres become trophoblasts which become placenta, inner blastomeres become inner cell mass
11
Q
What layer is used for embryonic splitting?
A
inner blastomeres,
makes more individuals
12
Q
zona pellucida
A
outer layer surrounding the zygote
Stays in place while cell number increases and cell size decreases
13
Q
gastrulation
A
gives rise to the three germ layers and marks the beginning organ and body development
occurs at about 2 weeks of development
determines polarity of head/tail and right/left
14
Q
how is the yolk sac different from a chicken yolk
A
yolk sac does not contain as much yolk
15
Q
layers of bilaminar disc? Which is smaller?
A
Hypoblast is smaller than epiblast
16
Q
Formation of three germ layers
A
Primitive streak becomes primitive groove.
Epiblast cells flow toward primitive groove. Some do deep to form endoderm, some intermediate to form mesoderm, and some do not go through primitive groove to form ectoderm
Some cells go through primitive node instead to develop notochord by streaming cranial
17
Q
mesoderm
A
muscle, skeletal tissue, urogenital, and cardiovascular
18
Q
endoderm
A
lining of the digestive and respiratory tracts plus organs of digestion
19
Q
ectoderm
A
epidermis, neural tissue and some skeletal//connective tissue of the head
20
Q
somatic mesoderm
A
give rise to body/body wall
They grow ventrally and meet together to close the body wall/ coelom
21
Q
splanchnic mesoderm
A
give rise to organs
grows ventrally at smaller radius than the somatic mesoderm to enclose the primitive gut tubeq
22
Q
schistosomus relexus
A
somatic mesoderm does not close, can survive in utero, but not postnatal
most common in cattle
23
Q
amorphous globosus
A
free, asymmetrical twin, not sure what causes it
24
Q
monozygotic twinning
A
identical twinning
3 types:
1. Twinning at 2-4 cell stage, completely separate placentas and blastocysts
2. Morula forms two masses with one trophoblast layer. Shared placenta with separate amniotic cavities
3. Near gastrulation, tow primitive streaks are formed. Shared placental units and shared amnion. Umbilical cords can loop around other twin’s neck.
25
conjoined twins
if masses do not split from two primitive streaks
26
white matter
contains neuroglia and axonic projections
27
first organ system to initiate differentiation
central nervous system
| Not the first to become functionally differentiated
28
Neural tube formation
a few days after gastrulation
notochord produces factors that drive ectoderm to form neural plate. Mesoderm and ectoderm rise up to form neural folds while neural groove sinks down between
Neural folds reach out and contact each other. Neural tobe separate from surface ectoderm and descends into embryo. Neural tube cavity joins with amniotic cavity through rostral and caudal neuropore. These close about 1-2 days after cardiovascular system is functional. Issues if no closure.
Closure can be in these stages all along the tube at the same time
Begins in cervical area and progresses in both directions (so abnormal segments can develop between normal segments)
29
importance of neural tube cavity
no cardiovascular system set
30
neural crest cells
separate from surface ectoderm. derived from ectoderm
| give rise to ganglia, Schwann cells, and adrenal medulla
31
alar plate
sensory
32
basal plate
motor and autonomics
33
mantel layer
includes alar and basal plates. Neurons in this layer project axons into the marginal layer.
34
autonomic neruons
visceral motor neurons
35
spinal cord formation
alar and basal plates expand in all directions
Alar becomes dorsal horn. Basal becomes ventral horn. Roof and floor plates do not move much, resulting in dorsal sulcus and median fissure
36
ventral root formation
neuronal cell bodies of ventral horn projects axon into the periphery, forming ventral root. The axons from the motor neuron find target.
37
dorsal root formation
cells migrate to ganglion and project axon two ways to target and spinal cord.
38
functional connection
neuron requires functional connection on both ends and become integrated into a system.
More neurons are produced than those that become successful as some do not make functional connection.
39
positional changes of the spinal cord
in early development, spinal cord completely fills vertebral column
sipinal nerves come out of vetebral column and come into contact with bundles of muscle (somites).
Vertebrae grows faster so spinal cord moves relatively cranially, causing spinal nerve roots to elongate. (Need to maintain contact with muscle to survive)
40
cauda equina
many rootlets within spinal column that look like a horse tail
41
spina bifida
caused by tissue with formation of neural tube. Always results in vertebral arch malformation
42
spina bifida occulta
most benign, only effects 1-2 vertebrae
43
myeloschsis
more severe ane neural tube fails to form
44
meningomyelocele
meninges have herniated to where vertebrae should be. Can stand with help. Paresis or Paralysis
45
3 Primary vesicles
Forebrain, midbrain, hindbrain
46
aqueduct
narrower brain cavity
47
brain malformations
cerebellar hypoplasia, anencephaly, lissencephaly, cranium bifidum, hydrocephalus
48
brain vesicles
develops from rostral end of neural tube. Mantle and Marginal layers still present in the wall.
49
nucleus
collection of neuronal cell bodies in the CNS
50
cerebellar development
neurons in external germinal layer undergo a lot of division until they separate from external germinal layer and migrate into cerebellum
As migrating cells descend they integrate with Purkinje neuron axons to make future synaptic junctions
51
Where are the cells of of the cerebellum derived from?
external germinal layer
52
How do viruses like BVD and feline panleukopenia cause cerebellar hypoplasia?
They target external germinal layer, which also causes Purkinje cells to die off.
53
Where ventricles derived from?
central cavity
54
development of cerebrum and diencephalon
cells in mantle layer divide and then are signaled to move through marginal layer to the outside. These cells continue to divide. Then there is a third migration of cells that move farther past this second layer. Cells are forming functional connections and communicating with the cells that have already migrated to make sure it is a good environment.
These migrations are why the grey matter is on the outside of the cerebrum, but inside of the spinal cord and allow for convoluted surface of the brain with sulcus and gyrus
55
common cause of anencephaly
disruption of closing rostral neural pore
56
lissencephaly
smooth cortex, less sulci and gyri, caused by arrested cell migration
57
encephalocele
cranium bifidum, disruption of neural tube formation
58
hydrocephalus
disruption of CSF flow out of brain to subarachnoid space from choroid plexus
59
posterior pituitary gland development
neuronal cell body in brain projects axon to the posterior pituitary.
Direct growth from floor plate to forebrain.
60
anterior pituitary gland development
For anterior pituitary, the axon goes to portal vein and releases neural substance that is carried to anterior pituitary through this vein. Upgrowth from roof of primitive mouth.
61
What germ layer gives rise to pituitary glands?
Both are from ectoderm
62
Adult heart organization
1. atria are beside each other and dorsal to the ventricles
2. Ventricles are beside each other
3. Configuration of the outflow: spiral around each other
63
Heart embryology
1st organ to functionally differentiate, first beats around the time of neural tube closure (18-19 days in dog, 35-38 hours in chick)
Moves blood from extra embryonic vessels through embryonic circulatory system
64
stages of heart development
cardiogenic plate, single median heart tube, the heart starts, cardiac loop, partitioning and valves
65
friquency of congenital cardiovascular anomaly in humans
8/1000 human births
66
development and folding of cardiogenic plate
begins development outside the embryo then brought in through 180 degree body wall folding and closure, goes to about where mandible would be in adult
67
when does heart beat start?
Fusing of endocardial heart tubes begins the heart beat from caudal to cranial with contractions
68
derivitives of truncus arteriosus and blubus cordis
ascending aorta and pulmonary trunk
69
bulbus cordis
part of the right (conus arteriosus) and small part of left ventricle
70
Primitive heart regions
truncus arteriosus and bulbus cordis, ventricle, atrium (becomes right and left atria), sinus venosus
Differential growth with no internal divisions
71
derivatives of sinus venosus
left coronary sinus, part of wall of the right atrium
72
cardiac loop
normal bending to the right caused by asymmetries in proliferative activity (differential growth)
allows bulbus cordis to lie next to the ventricle because this is where it contributes
By the end, atrium is dorsal to ventricle
73
atrioventricular canal partitioning
endocardial cushions divide the atrioventricular canal
74
atrial partitioning
development of 2 septa and 3 foramina
need to maintain right to left shunting of blood in the atrium then stop this shunting postnatally
Blood flow from right atrium, inbetween septum 2 then 1 through foramen ovale, to left atrium
75
first septum development
from dorsal part of atria to endocardial cushions and closing foramen 1
76
first foramen
opening between endocardial cushions and septum 1
77
second formamen
develops as foramen 1 closes to maintain shunting. Develops by apoptosis of semtum 1
78
second septum
develops ventral caudal along with foramin 3 (foramen ovale)
79
partitioning of truncus arteriosus and bulbus cordis
outflow separation between aorta and pulmonary trunk by spiral septum
Truncus arteriosus gives rise to majority of aorta and pulmonary trunk with some contribution from bulbus cordis
Cushions invade lumen of truncus arteriosus and grow together. Different orientations results
80
ventricular partitining
endocardial cushion grows down while interventricular septum grows upward and spiral septum seals interventricular foramen
There is still a foramen in the interventricular septum
One part of spiral septum fuses with interventricular septum and another part fuses with the partitioning of the atrioventricular canal
81
Dextrocardia
folding has been flipped around, so the right ventricle looks like the left and so on
82
situs inversus
entire body plan is flipped. Doesn't impact life. 1/10,000 humans.
83
Ectopic cordes
heart is outside the thoracic cavity either by being cranial to first rib or ventral to sternebra. Was not folded in correctly. Most commonly found in cattle
84
valvular defects
stenosis/narrow valve, insufficiency (valve did not form correctly and is leaking and blood can bypass it), dysplasia (abnormal development)
85
Tetralogy of Fallot
Intraventricular septal defect, pulmonary stenosis, dextroposition of aorta (overriding), right ventricular hypertrophy
due to uneven division of truncus arteriosus in spiral septum formation, resulting in uneven intraventricular septum formation.
Right ventricle is exposed to the higher pressures of the left ventricle and hypertrophies
86
pulmonary stenosis
narrowing of pulmonary trunk, aorta overrides right and left ventricular outputs
87
What facilitates the fetus to pump blood to the placenta?
Coupling the systemic outputs by having the ventricles by next to one another
88
fetus vs embryo
with a fetus, the species can be identified but not in an embryo
89
closure of umbilical arteries
dam chews off the umbilicus
90
closure of umbilical vein
due to loss of blood pressure and less prostaglandin E2
91
Fetal circulation
Umbilical vein carries oxygenated blood from placenta to liver. Here it either goes through tissue of liver to caudal vena cava, or go through shunt to bypass parenchyma of liver to cauda vena cava. Blood is now purple because it is mixing with low O2 blood in CVC.
1st route from CVC: through oval foramen between septa 1 &2 to left atrium then left ventricle and aorta.
2nd route: goes to right ventricle mixes with more low O2 blood from cranial vena cava and goes to pulmonary trunk.
Ductus arteriosus joins blood from pulmonary trunk with aorta.
Aorta descends into umbilical arteries.
92
which has more oxygen? umbilical vein or umbilical artery?
umbilical vein
93
closure of ductus venosus
usually before birth, but can also close due to changes in blood pressure and less prostaglandin E2
94
closure of oval foramen
left atrium has lower blood pressure than right atrium in vivo because right atrium is receiving more blood, As lungs expand the pressure on the left increases and right decreases because there is less placental return, pushing septum 1 into septum 2
95
closure of ductus arteriosis
drop in blood pressure and less prostaglandin E2, takes the longest to close, starting at birth to about 1-2 days after
96
prostaglandin E2
vasodilator
97
aorta in embryo
goes from 2 ventral and 2 dorsal aorta to one of each
98
5th aortic arch
only present in lower vertebrates
99
formation/ degeneration of aortic arches
Form sequential, 1st arch degenerates, dorsal aorta between arches 3 and 4 degenerate, making the 3rd responsible for head and 4th responsible for the body
100
derivatives of 3rd aortic arch
right and left internal carotid arteries
101
left 4th aortic arch
aortic arch in adult
102
right 4th aortic arch
right subclavian artery
103
left 6th aortic arch
ductus arteriosus
104
right 6th aortic arch
degenerates. Why? right side needs to have continuation of developing GI system
105
aortic coarctiation
constriction of developing aortic arch resulting in malformation
106
ligamentum arteriosum
adult remnant of ductus arteriosus
107
left 4th aortic arch becomes adult arch, left 6th aortic arch becomes ductus arteriosus
normal
108
right 4th aortic arch becomes adult arch, right 6th aortic arch becomes ductus arteriosus
right to right connection and animal can function normally
109
right 4th aortic arch becomes adult arch, left 6th aortic arch becomes ductus arteriosis
normal function during suckling phase, but issues with solid food because vessels are wrapping around the esophagus and food cannot pass through
110
urogenital ridge
forms urinary and reproductive system, made from intermediate mesoderm and coelomic mesothelium
111
Which early kidney becomes adult kidney?
Metanephros, but there is remnants of pronephros and mesonephros
112
pronephros
7-8 tubules, non-functional, pronephric duct persists as the mesonephric duct, develops in cervical area/ embryologic neck
113
mesonephros
consists of 70-80 tubules, tubules
look similar to pronephric tubules, have glomerulus at one end connected to the mesonephric duct at the other, rapidly degenerates from cranial to caudal
114
derivatives of caudal tubules of mesonephros
caudal tubules and duct remain to form testicular channels, epididymis, ductus deferens and contributes to gonad development in both sexes
115
metanephros
adult kidney, consists of metanephric diverticulum (ureteric bud) and metanephrogenic mass (mesenchyme). Metanephric diverticulum come off mesonephric duct and continues as the metanephrogenic mass
116
derivatives of metanephric diverticulum
ureter, renal pelvis, calyxes and collecting ducts
117
derivatives of metanephrogenic mass
nephrons: functional unit of kidney that produce urine. Production stops just before or just after birth and never restarts. Cannot be replaced in adult, lost with age
118
variation in macroscopic apearance
unfused lobes in cow
| variation resulting from interactions between metanephric diverticulum and metanephrogenic mass
119
development of urinary bladder
Urinary bladder develops from expansion of the urachus and cranial end of the urogenital sinus
120
urogenital sinus
cranial portion forms bladder along with urachus
| Caudal portion forms pelvic and penile urethra in male, and pelvic urethra, vestibule and caudal vagina in female
121
Duct incorporation and reorganization
metanephric diverticulum starts out not opening into the bladder, then bladder grows dorsally to incorporate these tubules so that mesonephric duct which becomes ductus deferens opens closer to the urethra and ureter opens into the bladder.
This swapping results in the trigone region
122
urachus
channel from cranial urinary bladder down the allantoic stalk that opens into the allantoic cavity. Closes around time of birth
123
renal agenesis
kidney fails to develop
124
renal dysplasia
abnormal growth, eg. Horseshoe kidney
125
renal hypoplasia
kidney does not develop to full size
126
ectopic kidneys
normally, differential growth moves kidney from pelvis to sublumbar location.
ectopic kidneys remain in pelvis
doesn't result in many issues until animal might become pregnant, putting a lot of stress on the kidney
127
patent urachus
urachus does not degenerate, increased risk of umbilical infections
128
Why is the urachus needed?
there is a membrane covering the urogenital sinus to prevent urine from leaving into amniotic cavity
Later this membrane breaks down and urine can leave into allantoic and amniotic cavities
129
early reproductive development
mesonephric duct is retained in the male, paramesonephric duct associated with female development
gonad and external genitalia are able to develop into either sex at this point
130
hormones in male differentiation
Testis produces Mullerian inhibiting substance from sertoli cell to suppress paramesonephric duct and testosterone from leydig cells so mesonephric duct is stimulated to form ductus deferens and epididymis. Testis also produces dihydrotestosterone that stimulates external genitalia to produce penis, scrotum, prostate, seminal vesicle, and bulbourethral gland
131
hormones in female differentiation
ovary produces estrogens, including from maternal and placental sources to stimulate paramesonephric duct to form uterine tube, uterine horn, body, cervix, and cranial portion of vagina, and stimulates external genitalia to form labia, clitoris, and caudal portion of vagina
132
Primordial germ cells
develop in caudal portion of yolk sac, population of 100-300 cells. Then they migrate through hindgut and messentey to form genital ridge immediately ventral to mesonephros
133
genital ridge
primordial germ cells undergo replications.
134
gonadal cords
formed by disintegrating mesonephric tubule epithelium and primordial germ cells form seminiferous tubules
135
efferent ductules
small sperm conducting parts of testicle
136
formation of testis
rete testis and efferent ductules are derived from mesonephric tubule.
Mesonephric duct becomes ductus deferens and epididymis
137
Gubernaculum
```
mesenchymal tissue (embryologic connective tissue) between the testicle and scrotum.
Influences extracellular matrix to produce hyaluronic acid to increase water and well to dilate inguinal canal and scrotum. Mesenchymal cells then decrease hyaluronic acid and water to make gubernaculum shrink and pull testicle into the scrotum
Tethers the testicle in location. Becomes ligament of the tail of the epididymis and the proper ligament of the testes
```
138
ovarian development
gonadal cords break down to surround oocyte to form follicular cells
Ended by birth
139
variation in uterine morphology
due to differing fusion of paramesonephric ducts
140
uterus didelphys
No fusion between paramesonephric ducts, 2 uteruses and vaginal cavities, normal in marsupials
141
vagina simplex uterus duplex
some fusion of paramesonephric ducts, rabbits and rodents, two uteruses and two cervixes, one vagina/ vaginal cavity
142
uterus bicornis
2 uterine horns with a fused body cranial to singular cervix, one vagina
143
is the cervix considered a part of the vaginal cavity, uterus, or neither?
uterus
144
Which animal has the greatest degree of paramesonephric duct fusion in domestic animals?
Horse
145
primate uterus
completely fused paramesonephric ducts with just a uterine body
146
urogenital folds
help form ventral aspect of penile part of male urethra and labia of the vulva in female
147
labioscrotal swellings
give rise to labia majora in human females, which is not present in domestic animals.
Gives rise to scrotum in male
148
erectile tissue
corpora cavernosa and corpus spongiosum in male penis, corpora cavernosa in female clitoris
149
genital tubercle
forms Glans clitoris or penis, erectile tissue and the bulb of the vaginal vestibule
150
cloaca
sewer, present in non mammals after birth
closed by cloacal membrane
Urorectal septum forms at junction of hindgut and urogenital sinus to divide the cloaca. Grows caudally and divides cloacal membrane into anal membrane and urogenital membrane, which both break down in normal development
151
anogenital distance
distance between anus and glans, this is shorter in the female
152
malformation of genitalia
Hypoplasia or aplasia: few or no germ cell, respectively
Cryptorchidism: interruption of testicular descent, retained testicle, could be one side or bilateral
Stenosis (narrowing) of ducts and abnormal fusion.
Hypospadia: open urethra, penile part of male urethra does not close, incorrect formation between urogenital sinus and urogenital folds.
Intersex conditions
153
testicular feminization
not uncommon in pigs, XY chromosome but not enough testosterone produced in utero to cause differentiation or testosterone receptors are defective, anogenital distance is increased compared to female
154
Does male or female differentiation occur earlier?
male differentiation beginning with paramesonephric duct
155
Fee martin
Most commonly in cattle, dizygotic twins with one male and one female
Blood supplies of developing twins join together 95% of the time and hormones pass between. Female is most severely impacted because male differentiation begins first. Derivatives of paramesonephric duct are impacted the most.
156
Foregut fermenter
ruminants, stomach (rumen) is greatly enlarged. Microbial fermentation takes place in non glandular chambers, abomasum is glandular. Still some fermentation in hindgut.
157
which section of the GI tract is enlongated in horse?
ascending colon
158
spiral colon
ascending colon of ruminant,
| also found in swine but with different physiology between large ruminants, small ruminants and swine.
159
Foregut derivatives
esophagus, stomach, descending duodenum, liver, and pancreas
160
midgut derivatives
ascending duodenum, jejunum, ileum, cecum, ascending and transverse colon
161
hindgut derivatives
descending colon
162
simple stomach
differential growth of the dorsal wall
90 degree rotation around the longitudinal axis of the dorsal portion to the left (anticlockwise)
Rotation around a dorsoventral axis: caudal end of the stomach shifts to the right and cranially
In embryo: straight tube from mouth to cloaca. Dorsal wall grows fastest, causing the rotation
163
directionality of GI tract
descending duodenum is always on the right fundic part of stomach projects to the left
164
mesenteries
all organs supported by mesentery in early development
| Dorsal mesogastrum/greater omentum grows to allow rotation of gut during development
165
Which mesentery elongates to allow for rotations of the stomach?
dorsal mesentery, ventral does not elongate
| Dorsal mesentery folds in on itself to create 2 leaves of greater omentum
166
ruminant stomach
rumen develops as an expansion of the fundus. Project to left body wall.
reticulum is cranioventral pocket of developing rumen. Also on the left
Omasum develops as a bulge along the lesser curvature, projects to right body wall.
Abomasum is the remainder of the stomach, location is variable
167
development of midgut
supported by elongated dorsal mesentery and cranial mesenteric artery
Cecum forms as evagination of caudal limb of loop
Loops towards umbilicus and yolk sac, herniates into the yok sac because the liver is so large during development
168
Flow of ingesta in intestines
in caudal duodenal flexure, injesta flows from right to left caudal to mesenteric root. In transverse colon, ingesta flows from right to left cranial to mesenteric root
169
rotation of intestines
occurs in physiologic hernia, stomach has already undergone its rotation.
Cranial limb undergoes explosive growth and passes to the right of cranial mesenteric artery. Pushes the caudal limb cranially. Growth of cranial limb continues in cranial direction, moving caudal limb to the right side. Herniated viscera drawn back into body cavity. Ends with 270 degree rotation around cranial mesenteric artery forming mesenteric root.
170
intestinal stenosis
narrowing of intestinal lumen due to narrowing during recaulization when it should expand
171
intestinal atresia
during twisting of intestine, part of blood supply become compromised resulting in missing section
172
atresia ani
anal membrane does not break down
173
urorectal fistula
issue in separating urogenital sinus from rectum and anal canal
174
Both atresia and urorectal fistula
defecation through the vulva, increased risk of urinary tract infection
175
basic elements of pharyngeal arches
aortic arch, cartilage rod, cranial nerve and muscle
176
structures derived from pharyngeal arches
face, mandible, maxilla, larynx, hyoid apparatus
177
Which is more? cranial nerves, or pharyngeal arches?
cranial nerves
178
1st pharyngeal arch
becomes trigeminal nerve (CN V), mandible, maxilla, incus, and malleus bones, muscles of mastication and rostral digastricus
179
2nd pharyngeal arch
becomes facial nerve (CN VII), hyoid and stapes bones, muscles of facial expression and caudal digastricus
180
3rd pharyngeal arch (FYI)
Glossopharyngeal nerve (CN IX), stylopharyngeus: dilator of pharynx
181
4th and 6th pharyngeal arches
CN X, Vagus nerve, laryngeal cartilage, 4th become cricothyroideus muscle and 6thh the remaining intrinsic laryngeal muscles
182
Where do the right and left recurrent laryngeal nerves turn around in the body?
Right around the right subclavian artery, left around the ligamentum arteriosum
183
nasal pit
depression that becomes nasal cavity
184
cleft lip
failure to close fissure between medial nasal process and maxillary process
185
oronasal cavity formation
oral and nasal cavities are freely communicating through oronasal cavity. Oronasal membrane breaks down. Nasal pits excavate caudally as well as medially to connect together. Primary palate forms from maxillary process to separate oral and nasal cavities and right and left nasal cavities.
186
oronasal cavity separation
abnormally large tongue regresses in size so secondary palate can have more horizontal orientation and grow together. This is a small time window, so if it doesn't close now, it stays open as cleft palate.
Nasal septum needs to grow down to contact secondary palate to separate right and left.
Secondary palates need to fuse with each other, as well as close primary palate.
Rostral 2/3 is soft membranous right after closure, then ossifies into hard palate.
187
prognosis for cleft palate
difficult to manage with higher incidence of pneumonia, so euthanized.
188
respiratory morphogenesis
esophageal and tracheal separation, Laryngotracheal groove is in ventral pharynx between pharyngeal arches 4 and 6. Trachea is being pinched off ventral part of esophagus
Sometimes separation does not occur
189
lung development
alveoli are late developing structure. Greatest percentage develop in postnatal period.
190
Why are there respiratory movements in utero?
If joint doesn't move in development, it won't move after birth. Also exercising respiratory muscles. These movements involve inhaling amniotic fluid that is expelled through lymphatics and capillaries
191
Pulmonary transition to postnatal life
during birth, need to expel amniotic fluid from lungs, and start breathing through gas exchange. Relies on normal presentation.
Once on the ground, the umbilical connection is lost and the lungs and alveoli need to expand to increase surface area for gas exchange and get rid of fluid.
Note: hanging animal by rear legs hinders expansion of lungs.
192
pulmonary hypoplasia
abnormal structure of pleural cavity
193
trachel hypoplasia
underdeveloped trachea, common in brachycephalic breeds
194
tracheoesophageal fistulas
connection between esophagus to trachea
