Topic # 9 Flashcards
The digestive system consists of
the mouth (oral cavity);
pharynx,
esophagus,
stomach;
and small intestine;
colon and cecum;
rectum; anal canal; and the liver,
pancreas, and salivary glands
The oral cavity is derived from , a depression of surface ectoderm cranial
to the pharynx
stomodaeum
The stomodaeum is separated from the foregut (pharynx) by the
oral plate or
oropharyngeal membrane
. At of chick embryo the stomodaeum
deepens following rupture of oral plate, to form the oral cavity that communicates w/ the
pharynx.
72 hrs of incubation
Structures Associated with the Oral Cavity (Mouth)
The structures associated with the oral cavity are the
lips, gums, teeth, tongue and
salivary glands.
is derived from maxillary process of VA 1 and medial nasal processes that form
Palate
two palatine primordia:
primary palate and secondary palate.
Formation of the primary palate occurs as follows
The right and left medial nasal processes
fused in the midline to form a small triangular
medial palatine process (primary palate) that becomes the
incisive bone
Formation of the secondary palate occurs as follows:, which meet at the midline, merging dorsally with the nasal septum and
rostrally with the primary palate.
lataral
palatine processes
Rostral two-thirds of the secondary palate ossifies to become
the that separates the nasal and oral cavities.
hard palate
Caudal third of the secondary
palate does not ossify and become the that divides the pharynx into dorsal
nasopharynx and ventral oropharynx.
soft palate
- cleft palate caused by failure of the median palatine process (primary
palate) and the lateral palatine processes (secondary palate) to close along the midline,
leaving a gap or cleft
Palatoschisis
are derived from the stomodeal ectoderm.
Lip and gums
They are formed as follows:
In the ectoderm lining the stomodeal cavity, an arc of the thickened ectoderm, the
labiogingival lamina
The lamina invaginates into
underlying ectomesenchyme, forming a
labiogingival groove
Tissue external to the groove forms the lip, and tissue medial to the groove forms the
gingiva
Fusion of upper and lower lips caudally
forms .
cheeks
An arc of periodically thickened ectoderm, situated
inside of the labiogingival lamina, constitutes the
dental lamin
Dental lamina invaginates to
form
dental bud.
Each
bud assumes a cup-shaped configuration becoming an
enamel organ
Ectomesenchyme within the concavity of the enamel organ forms a
dental papilla
The concave epithelial layer of the enamel organ induces ectomesenchyme of the dental
papilla to form an epithelial layer of that deposit the dentin of the tooth
odontoblasts
surrounding the enamel organ condenses into a dental sac
Ectomesenchyme
Ectomesenchyme surrounding the enamel organ condenses into a dental sac that
gives rise to three layers:
Outer cells of dental sac
Middle layer of dental sac
Inner cells of the sac
differentiates into osteoblasts that deposit bone of the
alveolus (socket receiving the tooth)
Outer cells of dental sac
differentiate into fibroblasts, that secrete collagen
fibers to form periodontal ligament that anchors the tooth within the
alveolar socket.
Middle layer of dental sac
become cementoblasts that secrete cementum (modified
bone) that adheres to the surface of the tooth, particularly the dentin
surface of the root of the tooth.
Inner cells of the sac
develops from four swellings (2 distal, 1 median and 1 proximal tongue
swellings) situated on the floor of the pharynx.
Tongue
The body of the tongue arises predominantly from
median tongue swelling or (ectomesenchyme of VA1)
tuberculum impar
The root of the tongue is formed by the (ectomesenchyme of VA3) and covered by endoderm of the pharynx
(foregut)
proximal
swelling or copula
are derived from stomodeal ectoderm
Salivary glands
is derived from the cranial part of the foregut.
pharynx
becomes the remaining small intestines (caudal duodenum, jejunum and
ileum), cecum, ascending colon, and part of the transvers colon
Midgut
becomes transverse and descending colon and a cloaca which forms the
rectum and most of the anal cana
Hindgut
The foregut becomes flattened or compressed laterally and presents in sequence 5
bilateral outpocketings of its endoderm to form the walled in by a series
of visceral arches
pharyngeal pouches
A midline evagination of the floor of the pharynx gives rise to the
laryngotracheal groove.
MALFORMATIONS OF PHARYNGEAL POUCHES
Brachial cyst
Brachial sinus-
Brachial fistula
epithelial-lined brachial cavity that does not open unto the skin surface.( no
opening)
Brachial cyst-
epithelial-lined brachial cavity that opens unto the skin surface or into the
pharyngeal pouch. (one opening
Brachial sinus-
- epithelial-lined brachial cavity that opens to both the skin surface and the
pharyngeal pouch. (two openings).
Brachial fistula
develops from a tubular segment of the Foregut, Caudal to the
Pharynx
Esophagus
Development of Stomach
A. Simple Stomach
B. Ruminant Stomach -
is present in most domestic mammals. This develops from a tubular
segment of foregut caudal to the esophagus.
Simple Stomach -
= left of the midline
Cardiac end
= right of midline
Pyloric end
Two rotations are involved:
First rotation is 90⁰
2nd rotation is also 90
Greater omentum becomes folded creating a blind cavity called the
omental bursa
the peritoneal cavity via an opening the (foramen of Winslow).
gastroepiploic foramen
- consists of three compartments (rumen, reticulum, and omasum)
and one glandular compartment (abomasum
Ruminant Stomach
The develops as an expansion of the fundus
rumen
of the developing rumen forms the reticulum.
caudoventral pocket
The develops
as a bulge (ventral sac) along the lesser curvature
omasum
The intestinal tract consists of the [duodenum (divided into descending and
ascending regions),
small intestine
[colon (divided into ascending,
transverse, and desce
large intestine
The small intestine is derived from the (cranial duodenum) and (caudal
duodenum, jejunum and ileum).
foregut and midgut
the dorsal mesentery that suspends the
expands and the right vitelline artery (adult cranial mesenteric artery)
courses through it
intestinal loop
After the loss of the yolk stalk the intestinal loop rotates around
the cranial mesenteric artery to form the root of the mesentery.
360⁰ twice
The cranial limb of the loop
expands to form the coiled .
The caudal limb of the loop becomes
jejunum
The of the loop becomes the ileum and gives off the cecum
caudal limb
The caecum and colon show extensive developmental changes in different species of
domestic animals, except
dog and cat.
dog and cat the is small and coiled.
caecum
ruminants the caecum is and dilated and located on the right side of dorsal
abdomen.
straight
In the the caecum enlarges so that the proximal colon is incorporated within the cecum.
The cecum is located on the right side of the abdomen.
horse
Among the different parts of the colon, the shows the most extensive
change
ascending colon
of ascending colon of ascending colon forms distal to the cecum:
secondary loop
In the secondary loop coil forming the spinal colon which is shaped like a
pyramid in pig and like a coiled rope in ruminant
pig and ruminant
is the terminal part of the hindgut, a chamber that communicates with the
digestive, urinary and genital systems.
cloaca
The caudal wall of the cloaca is formed by
cloacal membrane
a septum formed by
the apposed endoderm of the hindgut and of the proctodaeum.
surface ectoderm
is the depression of the surface ectoderm under the root of
the tail and is the counterpart of stomodeum in the oral region
proctodeum
The derived from the cloaca
rectum
of the anal canal (most of the canal) is formed with the rectum; part
of the anal canal is lined by a mucosal epithelium derived from endoderm.
o The caudal part of the anal canal is derived from the proctodaeum it is
cranial part
Tissues surrounding the anal membrane grows caudally creating a depression
called the .
proctodeum
carnivores, lateral diventicula of proctodeum ectoderm become
anal sacs
arises as a hepatic diverticulum of endoderm from the region of foregut that
will become descending duodenum.
liver
develops at the end of the cystic duct.
gallbladder
One diverticulum (ventral pancreatic diverticulum) arises ventrally as a bud of the hepatic
diverticulum, it forms .
the pancreatic duct and right lobe of the pancreas
The other diverticulum (dorsal pancreatic diverticulum) arises dorsally from the duodenum
(minor duodenal papilla) and forms the accessory
pancreatic duct and the left lobe of the
pancreas.
*As the right and left lobes cross one another during development, they fuse to form the body
of the
pancreas
the duct system anastomose to form a
common bile duct.
, which develops as a diverticulum of the esophagu
crop
A two compartment stomach:
Proventriculus
Ventriculus or gizzard
are formed by splanchnic mesoderm when the embryonic gut is created as the
embryo assumes a tubular shape
Mesenteries
is separated from somatic mesoderm by the embryonic coelom
Splanchnic mesoderm
develops within the greater omentum.
As the midgut elongates and rotates around the
spleen
MALFORMATION OF THE DIGESTIVE SYSTEM
Meckel’s diverticulum
Atresia of the jejunum, ileum, colon, rectum
Atresia ani or imperforate anus
Urorectal Fistula
Umbilical hernia
– an appendix-like remnant of the yolk stalk that persist, may cause
inflammation and rupture resulting in colic with peritonitis.
Meckel’s diverticulum
– a lack of epethilial canalization and gut
wall development.
Atresia of the jejunum, ileum, colon, rectum
failure of anal membrane to break and remain patent .
Caused by lack of involution of the cloacal membrane and leads to fetal feed impaction
Atresia ani or imperforate anus –
abnormal developed of urorectal folds that allows communication
between the rectum and urogenital sinus
Urorectal Fistula –
muscular defect in the umbilical that allows abdominal organs to
protrude through the umbilical underneath the skin. Maybe inherited.
Umbilical hernia –
The stomodaeum is separated from the (pharynx) by the oral plate or
oropharyngeal membrane,
foregut
The further deepens by growth of surrounding structures
oral cavity
The oral
cavity is bordered cephalically by frontal prominence and by medial nasal,
maxillary and
mandibular processes
the tooth is composed of the
enamel, dentin, dental pulp and cementum
are derived from stomodeal ectoderm and ectomesenchyme (neural crest) of
VA1
Teeth
The inner concave
epithelium of the enamel organ differentiates into columnar ameloblasts that secrete the tooth
.
enamel
The
odontoblasts induce the concave epithelium of the enamel organ to differentiate into
that form enamel of the crown of the tooth
ameloblasts
The
remaining ectomesenchymeal cells of the differentiate into a loose connective
tissue with blood vessels and nerves (sensitive part of the tooth).
dental pulp
becomes flattened or compressed laterally and presents in sequence 5
bilateral outpocketings of its endoderm to form the pharyngeal pouches walled in by a series
of visceral arches
foregut
mammals, is rudimentary and appears as a diverticulum of PP4
PP5
