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List 9 derivatives of the fore-gut

• Part of the mouth
• Pharynx
• Oesophagus
• Stomach
• Liver and pancreas
• Major portion of the small intestine
• Thyroid, parathyroid
• And thymus glands
• Trachea and lungs


derivatives of the hind-gut

Terminal end of the small intestine and the large intestine and cloaca
Anal canal/urogenital sinus


2 structures involved with the development of the mouth and what each form

1) The Stomodaeum is a midline depression on the ventral surface of the head that is created by the cranial and lateral body folding.
○ enlarges into a definitive oro-nasal cavity. - the mouth and nose
2) The Oral Plate (or pharyngeal membrane) is formed by the fusion of the ectoderm of the stomodaeum and the endoderm of the fore-gut.
○ The oral plate subsequently breaks down and the cranial opening of the digestive tube is established.


branchial arches what derived from what does 1st branch, 2-3 branch and 4-6 branch create

1st branchial arch divides into the
left and right maxillary processes and mandibular
processes which elongate to form the jaws and mouth - oral cavity
2-3 hyoid bones
4-6 pharynx


mesenchymal process what called what includes and what forms

fronto-nasal prominences - and they will give rise to the future frontal area of the embryo and the nose.
○ This includes the Frontal process (will give rise to the frontal bones-the forehead) and the left and right naso-lateral and naso-medial processes (will give rise to the nose).


what forms the upper jaw, nose, lower jaw

The upper jaw - is formed by the naso-medial processes together with the maxillary processes
The nose - is formed by the frontal process together with the naso-lateral processes
The lower jaw - is formed by the fusion of the mandibular process in the midline


facial cleft, cleft lip and cleft palate failure of what fusion

Facial cleft (lamb)
–Maxillary and lateral nasal processes fail to fuse
Cleft Lip
–Maxillary and medial nasal processes fail to fuse
–May occur in association with cleft palate
cleft palate
- failure of the palatine processes to fuse


the palate derives from what three parts and how occurs

1) Left palatine process
2) Right palatine process
3) Median palatine process (= inter-maxillary process)
- These three processes fuse together to separate the oral and nasal cavities.
- This hard palate extends caudally as the soft palate that separates the rostral pharynx into the nasopharynx (dorsal) and oropharynx (ventral)


tongue formation what 4 mesenchymal swellings and what occurs

1. Median tongue swelling;
2 and 3. Two distal tongue swellings;
4. Proximal tongue swellings
1) The median and distal tongue swellings will form the body of the tongue,
2) the proximal tongue swelling will form the root of the tongue.


formation of the oesophagus what forms it, what forms epithelial lining, connective tissue and muscle layer

- The fore-gut narrows to form the oesophagus
- The epithelial lining of the oesophagus and any associated mucosal glands develop from the endoderm of the primitive fore-gut.
- connective tissue and muscle layer of the oesophagus are derived from accumulating mesenchymal cells partially derived from the splanchnic mesoderm of the primitive gut.


formation of the stomach

- A dorsal mesentery (the dorsal mesogastrium - greater omentum) develops on the dorsal surface and the ventral mesentery (the ventral mesogastrium - lesser omentum) develops on the ventral surface.
- The developing stomach moves caudally and shifts away from the midline.
○ Thus the stomach rotates towards the left pulling with it the dorsal mesentery and leading to the formation of the greater omentum.


4 steps in the formation of the small and large intestines

1) Initially the gut grows faster than the body so a hairpin-shaped loop is formed. The remnant of the yolk sac (the yolk-stalk) is at the tip of the loop.
2) Rapid development of the liver forces the loop of gut into the umbilical stalk - this is physiological herniation.
3) Later the intestines return to the abdomen and move into their final position.
4) Further changes involve rotation of the loop and extensive coiling of the cranial arm of the loop to form the duodenum, jejunum and most of the ileum.


formation of the anal opening from cloaca and proctadeum

- The caudal portion of the primitive gut expands to form the blind cavity of the cloaca.
- The invagination of ectoderm beneath the tail forms the proctadeum.
○ This boundary between the endoderm and the ectoderm forms the cloacal membrane.
○ This degenerates to form the anal opening.


Body cavities what are they created from and what creates each of the 3 cavities

three membrane-bound cavities know as coeloms initially continuous with each other but later seperated
1) The pericardial coelom
- contains the developing heart
2) The Left and Right pleural canals
- contains the developing lungs
3) The peritoneal coelom
- contains the developing abdominal viscera


development of the diaphragm

septum transversum
○ Forms part of the diaphragm
○ Other part formed by pleuro-peritoneal folds and pleuro-peritoneal canals that join to form the diaphragm


what are the normal drainage routes for the peritoneal fluid

1) most peritoneal fluid drains via small stomata (pores) into diaphragmatic lymphatics that form a large plexus in the muscular part of the right ventral diaphragm - pleural plexus on the opposite side of the diaphragm - right lymphatic duct to the thoracic duct - eventual return to the right side of the heart
2) a small proportion of peritoneal fluid drains through the omentum and abdominal viscera via lymphatics and lymph nodes to the thoracic duct


What are the 4 normal functions of the mesothelial cells

1) line the peritoneal cavity (and the pleural cavity and pericardial sac) - create shiny protective layer
2) produce a polysaccharide that acts as a low viscosity lubricant
3) produce plasminogen activator that results in the lysis of fibrin
4) activated mesothelial cells are capable of phagocytosis


How do mesothelial cells respond to mild irritation

1) hypertrophy (an increase in size)
2) hyperplasia (an increase in number due to mitotic division)
3) metaplasia (altered differentiation) from a squamous to a cuboidal or columnar cell


What is the typical sequence of events following injury to the peritoneal surface and what is the repair not influenced by

1) debris removed by phagocytosis (macrophage and mesothelial cells)
2) wound heal via granulation tissue and reconstitution of the mesothelial layer (mitotic division) - repair not influenced by the size of the defect
3) if surface fibrin persists more than 3-4 days post-injury, granulation tissue bridges between the apposed viscera and between the viscera and the cavity wall - fibrous adhesion formation - permanent (dysfunction possible)


List 3 decompositional changes that are commonly observed in the peritoneal cavity of dead animals

1) diffusion of haemoglobin from lysing red blood cells
2) diffusion of bilirubin from the gall bladder, bile ducts and/or duodenum
3) gas bubbles may develop subserosally over the viscera and in the adjacent mesenteries and ligaments


Define internal hernia and external hernia

Internal Herniation
= displacement of viscera (especially intestines) through a normal or abnormal hole (foramen) within the peritoneal cavity without formation of a hernial sac
= displacement of viscera with the presence of a hernial ring through a natural opening in the abdominal wall (e.g. the vaginal ring at the inguinal canal) or an abnormal opening


what are the components of external hernia and list 5 examples

1) hernial sac (formed as a pouch of parietal peritoneum +/- a covering of skin and soft tissues)
2) a hernial ring (the opening in the abdominal wall)
3) hernial contents (usually part of the omentum, a segment of intestine +/- other viscera)
1) ventral hernia of the abdominal wall
2) umbilical hernia
3) inguinal hernia
4) perineal hernia
5) diaphragmatic hernia


List 3 common examples of internal herniation

1) herniation through natural foramina - incarcerations of the epiploic foramen
2) omental and mesenteric hernias - passage of intestine through tear in greater or lesser omentum
3) pelvic hernia - mainly after castration


what is the difference between a direct and indirect inguinal hernia

- indirect inguinal hernia (in which viscera herniate into the inguinal canal of the groin between the internal inguinal ring and the external vaginal ring
- direct (or false) inguinal hernia in which herniated viscera pass subcutaneously, outside the inguinal canal


what is the most common type of diaphragmatic hernia in domestic animals and usual cause

Acquired Peritoneopericardial diaphragmatic hernia usually caused by external abdominal trauma


List 5 potential consequences of abdominal trauma

1) introduction of bacteria from exterior or perforation of the gastrointestinal tract - septic peritonitis
2) Peritoneopericardial diaphragmatic hernia
3) ± leakage of bile or urine into the peritoneal cavity
4) +/- uterine rupture in pregnant animals
5) potential fatal haemorrhage into the peritoneal cavity


How would you distinguish an ante mortem from a post mortem perforation of the gastrointestinal tract?

post mortem rupture of viscera - ingesta tends to be localised close to the rupture site, without haemorrhage at the margins of the tear and without evidence of peritonitis


What is a common parasite that encysts in the peritoneal cavity of sheep?

cysticercus - the intermediate (metacestode) stage of taeniid tapeworms
- appears as a fluid-filled, thin-walled cyst into which the head and neck of a solitary tapeworm larva is invaginated


list 4 possible causes of haemoperitoneum

1) trauma especially to the liver, spleen or kidneys
2) spontaneous rupture of enlarged spleen or liver
3) rodenticide anticoagulant poisoning and other coagulopathies
4) rupture of any friable intra-abdominal or retroperitoneal neoplasm


list 2 main mechanisms by which ascites may develop and the examples within

1) reduced removal of peritoneal fluid - due to obstruction of lymphatic drainage
2) over production of peritoneal fluid
1. increased permeability of blood vessels within peritoneal cavity
2. hypoalbuminaemia (