Topic # 9 Flashcards by BARREDA CHIELA

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

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The oral cavity is derived from , a depression of surface ectoderm cranial
to the pharynx

stomodaeum

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The stomodaeum is separated from the foregut (pharynx) by the

oral plate or
oropharyngeal membrane

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. 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

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Structures Associated with the Oral Cavity (Mouth)
The structures associated with the oral cavity are the

lips, gums, teeth, tongue and
salivary glands.

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is derived from maxillary process of VA 1 and medial nasal processes that form

Palate

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two palatine primordia:

primary palate and secondary palate.

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Formation of the primary palate occurs as follows

The right and left medial nasal processes

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fused in the midline to form a small triangular
medial palatine process (primary palate) that becomes the

incisive bone

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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

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Rostral two-thirds of the secondary palate ossifies to become
the that separates the nasal and oral cavities.

hard palate

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Caudal third of the secondary
palate does not ossify and become the that divides the pharynx into dorsal
nasopharynx and ventral oropharynx.

soft palate

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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

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are derived from the stomodeal ectoderm.

Lip and gums

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They are formed as follows:
In the ectoderm lining the stomodeal cavity, an arc of the thickened ectoderm, the

labiogingival lamina

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The lamina invaginates into
underlying ectomesenchyme, forming a

labiogingival groove

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Tissue external to the groove forms the lip, and tissue medial to the groove forms the

gingiva

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Fusion of upper and lower lips caudally
forms .

cheeks

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An arc of periodically thickened ectoderm, situated
inside of the labiogingival lamina, constitutes the

dental lamin

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Dental lamina invaginates to
form

dental bud.

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Each
bud assumes a cup-shaped configuration becoming an

enamel organ

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Ectomesenchyme within the concavity of the enamel organ forms a

dental papilla

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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

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surrounding the enamel organ condenses into a dental sac

Ectomesenchyme

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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

Topic # 9 Flashcards

(102 cards)