The ingestion and absorption of nutritious food is essential for life

Digestive system

Food is utilized at a cellular level.

Defecation

WHICH OF THE FOLLOWING IS ESSENTIAL AFTER FOOD IS EATEN?

A CHEMICALS IN FOOD TRAVEL THROUGH SINUSOIDS

B MOVEMENT OF FOOD INGREDIENTS THROUGH PORTAL SYSTEMC ENZYMATIC PROCESSING IN LARGEST

ORGAN IN THE BODYD PASSAGE OF LIPIDS THROUGH DUCT IN

DIAPHRAGME ALL OF THE ABOVE

The digestive system includes the organs that ingest food, transport food, digest the food into smaller usable components, absorb the nutrients, and expel the waste products from the body.

The digestive organs collectively make up the gastrointestinal (GI) tract (alimentary canal). The GI tract organs include the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.

As long as food is in the long hose extending from the mouth to the anus, it is NOT technically in the body. Only when it is absorbed is it in the body.

An example is when you put your finger in the hole of a doughnut. Your finger is NOT in the doughnut. If you image your G.I. tract as an elongated doughnut, then you can see the similarity.

The accessory digestive organs do not form the long GI tube, but often develop as outgrowths from and are connected to the GI tract. These accessory organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas

Ingestion of food that will cause atherosclerosis.

Food must be mechanically and chemically reduced before it can be absorbed across the intestinal wall.

Ingestion and mastication

Swallowing. Note closure of epiglottis over entrance to larynx

Endoscopic view of intestinal secretions that aid in digestion

Digestion and absorption

Defecation to eliminate feces

Mouth receives food, masticates, and instigates swallowing

Mouth (oral cavity) is bounded anteriorly by the teeth and lips and posteriorly by the oropharynx. The roof is the hard and soft palates, while the floor contains the tongue and muscles covered with mucosa.

The oral cavity has two distinct regions: the vestibule (space between the cheeks or lips and the gums) and the oral cavity proper (region central to the alveolar processes of the mandible and maxillae

Oral cavity proper

Muscle of cheeks is primarily the buccinator

The lips (labia) are formed primarily by the obicularis oris. The gingivae (gums) help support the teeth. The superior and inferior labial frenulum extend from the lips to the gingivae.

The hard palate is formed by the palatine processes of the maxillae and the horizontal plates of the palatine bones. Transverse folds assist the tongue in manipulating food. The soft palate is mostly composed of skeletal muscle. The uvula and soft palate rise superiorly during swallowing to close of the nasopharynx. The palatine tonsils monitor ingested food and drink for harmful antigens.

Tongue, which is composed of skeletal muscle, assists in mastication, in swallowing, has taste buds, and helps with speech.

Lingual frenulum anchors the tongue to the floor of the mouth. Note location of submandibular salivary ducts that can squirt!

Lingual

Saliva (spit) contains amylase which breaks down starch to maltose. It also contains lysozyme, and antibacterial substance.

The parotid salivary glands are the largest salivary glands and are located near the ear, partially overlying the masseter muscle. The parotid duct travels parallel to the zygomatic arch and opens into the vestibule near the second upper molar.

Swollen parotid gland in child with viral mumps. This virus can also infect the testes.

The submandibular salivary glands are inferior to the body of the mandible. A submandibular duct opens from each gland in the floor of the mouth on the lateral sides of the lingual frenulum. These are the squirters used in “gleeking”!

“Gleeking” with submandibular gland at base of lingual frenulum

The sublingual salivary glands are inferior to the tongue. Each sublingual gland extends multiple tiny sublingual ducts that open onto the inferior surface of the oral cavity.

The facial nerve (CN VII) innervates the submandibular and sublingual glands

The glossopharyngeal nerve (CN IX) innervates the parotid glands

Parasympathetic innervation stimulates salivary gland secretion (anticipation of tasty food). Sympathetic stimulation inhibits normal secretion, which is why persons who are frightened experience the sensation of a dry mouth.

A tooth has an exposed crown, a constricted neck, and one or more roots that anchor it to the jaw. The roots fit into dental alveoli where they are bound to the surrounding bone by the periodontal ligaments to form a gomphosis joint.

Permanent teeth

Teeth. The third molar (“wisdom teeth”) are not shown.

Permanent teeth found on one quadrant of the mouth: 2 incisors, 1 canine, 2 premolars, 3 molars.

Trauma

Dental implant post

Dental implants are effective, but are very expensive

Tooth being mounted on post.

Pharynx is the funnel-shaped structure that connects the oral and nasal cavities to the esophagus and trachea.

The superior, middle, and inferior pharyngeal constrictors, composed of skeletal muscle aid in swallowing. The vagus nerves (CN X) innervate most of the pharyngeal muscles.

Peritoneal

Within the abdomen, some organs are completely surrounded by visceral peritoneum (intraperitoneal organs). And example is the stomach.

Within the abdomen, some organs lie behind the parietal peritoneum (retroperitoneal organs). An example is the pancreas.

Mesenteries are double-layered folds of the peritoneum that support and stabilize intraperitoneal organs.

The greater omentum (“fatty apron”) extends from the greater curvature of the stomach and then all the way down to cover most of the small intestine and inferior abdominal organs.

Greater omentum flipped back over chest to reveal underlying intestines

Note mesentery proper and mesocolon

Lesser omentum (omentum = “apron” in Latin) attaches the stomach and upper duodenum to inferior surface of liver.

The falciform (“sickle-shaped”) ligament attaches the liver to the inferior portion of the diaphragm and to the anterior abdominal wall.

The mucosa (mucous membrane) has absorptive and secretory functions. The submucosa has lymph vessels, blood vessels, mucin-secreting glands, and nerve plexuses.

The muscularis typically contains two layers of smooth muscle, which are responsible for peristalsis.

The outermost tunic may be either an adventitia (loose connective tissue) or a serosa (visceral peritoneum).

Esophagus connects the laryngopharynx to the stomach. It passes through the diaphragm via the esophageal hiatus.

The wall of the esophagus contains both skeletal and smooth muscle

There are two sphincters associated with the esophagus: superior esophageal sphincter and inferior esophageal sphincter

Defective lower sphincter

Read the clinical view in text

Acid damage to esophagus by acid reflux through defective lower sphincter

The J-shaped stomach stores food (the semidigested mass is called chyme), initiates the digestion of proteins, has only minimal absorption, and moves materials on to the small intestine.

Stomach

Close-up of pyloric sphincter and pyloric orifice

Gastric rugae allow stretching of the stomach

Note greater and lesser curvatures

Close-up of gastric rugae

Gastric cells and their secretions

Read about peptic ulcers in the clinical view in the text

EVERYTHING PAST THIS POINT IS EXTRA OR FOR EXAMS

Figure 26.13a

Acid damage to esophagus

Peristalsis

Gastrointestinal tract (G.I. tract or alimentary canal) and some accessory organs of digestion.

The juxtaposition of the anterior portion of two alimentary canals

Mouth also forms words and assists with passage of air

Lips are fleshy, mobile organs formed by the obicularis oris muscle

This painted rock star has a very loose lingual frenulum!

Close-up of opening of submandibular salivary glands at base of lingual frenulum. They can squirt long distances1

Vallecula (#6) at base of tongue

Vallecula between epiglottis and base of tongue

Periodontal disease

Stomach is located in upper left abdominal quadrant just inferior to the diaphragm.

Stomach ulcers are typically triggered by a the bacterium Helicobacter pylori

Acid reflux damage to esophagus

stomach

spleen

Figure 26.co

Figure 26.02

Figure 26.06ab

Figure 26.11

Figure 26.10

Mumps is usually mild in children, but may be severe and damaging in adults.

Cleft palate

The bacterium Helicobacter pylori is the most common cause of stomach ulcers.

A stomach ulcer which perforates the wall of the stomach could lead to inflammation of the peritoneal cavity (peritonitis).

Endoscopic view looking down through esophagus at lower esophageal sphincter in person with hiatal hernia. Note stomach lining protruding up through defective lower esophageal sphincter.