Digestive System

Functions of digestive system

• absorption

• digestion

• elimination

Segments of digestive/alimentary tract

• mouth

• pharynx

• esophagus

• glandular stomach

• small intestine

• large intestine

Digestive glands

• salivary gland

• liver

• pancreas

Accessory digestive structures

• teeth

• tongue

• cheeks

• lips

• palate

first segment of digestive tract bounded dorsally by the palate as well as the upper set of teeth, laterally by the cheeks, and ventrally by lower set of cheeks, tongue, and floor of mouth.

Mouth

• connects the mouth to the esophagus

• common passageway for food, water, and air

Pharynx

3 Apertures of pharynx

• oropharynx

• nasopharynx

• laryngopharynx

is found at the junction of these three apertures; serves as a common passageway for digestive and respiratory tracts/common passageway for food, water, air.

Pharyngeal proper

long, muscular tube which serves as a passageway for bolus.

Esophagus

 is an ingesta passing along the esophagus (slightly acidic or alkaline in pH).

Bolus

3 segments of esophagus

• cervical

• thoracic

• abdominal

Thoracic esophagus becomes abdominal esophagus upon passing the tube or across the ____________ the diaphragm (flap of muscle which separates thoracic from abdominal cavity).

Hiatus Esophagi

4 Layers of the esophagus

• t mucosa

• t submucosa

• t muscularis

• t adventitia

muscular belt which temporarily stores chyme.

Stomach

the ingesta in stomach (bolus mixture with gastric juice) this is strongly acidic due to presence of HCl

Chyme

4 parts of stomach

• cardia

• fundus

• body

• pylorus

Curvatures of Stomach

• greater curvatures

• lesser curvatures

2 sphincters that prevent backflow of ingesta

• cardiac

• pyloric

4 layers

• t mucosa

• t submucosa

• t muscularis

• t serosa

Components of digestive juice

• Pepsin

• HCl

Cell of gastric gland that secretes pepsinogen

chief cells

2 surfaces of stomach

• Parietal (facing outside abdomen)

• Visceral (facing internal organs)

• named after its relative diameter (relatively smaller in diameter than the large intestine).

•  tube which connects the stomach with the large intestine and it starts at the pylorus.

Small Intestine

Segments of small intestine

• duodenum

• jejunum

• ileum

1st and most thick segment wherein the bile duct and pancreatic duct empty the bile or biliary secretion (their contents)  as well as pancreatic juices respectively.

Duodenum

longest and most movable (most absorptive segment of small intestine)

Jejunum

• terminal or the last segment of small intestine;

• has a certain role of defenses of intestine against microorganism which is possible due to the presence of peyer’s patches (lymphoid nodules/structures with support defenses or protection against microorganisms).

Ileum

Layers of Small intestine

• tunica mucosa

• tunica submucosa

• tunica muscularis

• tunica serosa

•  extends from the termination of ileum to anus.

• Has a much greater diameter than the small intestine

Large intestine

3 segments of large intestine

• cecum

• colon

• rectum

• counterpart of appendix in human

• vestigial/rudimentary structure in man

• serves as the site of fermentation in some animals, especially in post-gastric fermenter animals.

• In ruminants, microbial fermentation occurs in the rumen, whereas for rabbits and horses it happens in the ______.

Cecum

longest segment of large intestine and the main site for water and electrolyte absorption

Colon

terminal or last segment; serves as temporary storage site for food or the feces prior to defecation

• terminal segment of alimentary canal which 

• has sphincter muscles: sphincter ani externi et interni

Anus

3 pairs of large glands situated at the sides of the face and the adjacent part of the neck

Salivary glands

Salivary glands

• parotid

• submandibular

• sublingual

In most dominant animals and humans, how many salivary glands are present

3

Dogs have a 4th salivary gland called?

• located near/adjacent to the zygomatic bone or present at the level of the orbital cavity

Zygomatic gland or Orbital gland

Glands are classified according to the types of secretion:

• serous

• mucous

• mixed

an accessory salivary gland situated in the interior part of pterygopalatine fossa and is mixed type salivary secretion

Zygomatic Gland

• nutritional guardian of the body

• largest gland of the body

• situated obliquely against the visceral surface of the diaphragm

Liver

Lobes of the liver

• left hepatic

• right hepatic

• median/quadrate

• caudate lobe

Surfaces of the liver

• visceral

• parietal

In dogs the liver presents how many lobes?

7-8

divides into right medial and right lateral

(nasa caudal aspect) presents a papillary process, so it separates

caudate lobe

divides into the left lateral and left medial

left lobe

gland situated between duodenal loop

pancreas

2 portions of pancreas

• exocrine

• endocrine

Exocrine secretion of pancreas

• amylase

• lipase

• trypsinogen

• chymotrypsinogen

Endocrine secretions of pancreas

• glucagon

• insulin

essential for chopping, grinding, and chewing the food

Teeth

4 types/classification of teeth

• incisor

• canine

• premolar

• molar

no molar teeth present (only present in  permanent dentition)

deciduous

surfaces of teeth

• occlusal

• labial

• lingual

layers of teeth

• cementum - outer layer of neck

• pulp cavity - inner layer

• enamel - next to enamel

• dentine - outer layer of crown

Regions of teeth

• crown

• neck

• root

the cutting teeth of dogs with 3 roots

Carnassial teeth or cutting teeth/shearing teeth

supported in a muscular sling formed by the mylohyoid muscles.

Tongue

Parts of tongue

• root

• body

• apex

 refers to the free dorsal surfaces

Dorsum of tongue

mucous membrane of dorsum

papillated (lingual papillae)

Lingual Papillae

• filiform - bristle like

• fungiform - mushroom shaped

• foliate - leaf shaped (dog)

• vallate - v-shaped

described as having a base and free boarder

soft palate

2 surfaces of soft palate

• oral

• aboral

2 short thick folds which run from the free border of the oral surface to either side of the tongue (malapit sa oral surface)

anterior pillar

runs from free border to aboral surface

posterior pillar

 bounded in front and on either side by the alveolar arches.

Hard palate

The bony basis is formed by the palatine process of:

• pre-maxilla

• maxillae

• horizontal part of palatine bones

Largest organ

skin

Organ vs Gland

gland has excretion

Lightest organ

Lungs - dues to air spaces in lung parenchyma