Why do we eat??

Extracellular digestion

Health and Social Issues

Food is not technically in the body until it is:

• a. masticated

• b. ingested

• c. swallowed

• d. digested

• e. absorbed

How many people die from starvation?

How widespread a problem is malnutrition?

• More than 25,000 people die of starvation every day!

• If we were to add the next two leading ways the poorest of the poor die, water borne diseases and AIDS, we would approach 50,000 deaths per day.

What happens during starvation

• The United States has the highest rates of obesity in the developed world. From 1980 to 2002, obesity has doubled in adults and overweight prevalence has tripled in children and adolescents.

• From 2003-2004, "children and adolescents aged 2 to 19 years, 17.1% were overweight...and 32.2% of adults aged 20 years or older were obese."

• Complications of obesity include: diabetes mellitus type 2, high blood pressure, high blood cholesterol, and triglyceride levels. An inflammatory state is present, which — together with the above — has been implicated in the high prevalence of atherosclerosis (fatty lumps in the arterial wall), and a prothrombotic state may further worsen cardiovascular risk.

• Several additional health risks

Body Mass Index (BMI)

• A BMI less than 18.5 is underweight

• A BMI of 18.5 - 24.9 is normal weight

• A BMI of 25.0 - 29.9 is overweight

• A BMI of 30.0 - 39.9 is obese

• A BMI of 40.0 or higher is severely (or morbidly) obese

• Charts and calculators online for calculating BMI.

• My BMI is 25.1—I am in the overweight category!

• Bulimia is often less about food, and more to do with deep psychological issues and profound feelings of lack of control.

• Binge/purge episodes can be severe, sometimes involving rapid and out of control feeding that can stop when the sufferers "are interrupted by another person" or when their stomach hurts from over-extension.

• This cycle may be repeated several times a week or, in serious cases, several times a day.

• 90% of patients who suffer from this disorder are women. There are higher rates of eating disorders in groups involved in activities that put an emphasis on thinness and body type (such as gymnastics, dance and cheerleading).

• Some people may vomit automatically after they have eaten any food. Others will eat socially but may be bulimic in private. Some people do not regard their illness as a problem, while others despise and fear the vicious and uncontrollable cycle they are in

• The anorexic is more likely to believe they are in control of their eating and much less likely to admit to needing help, or that a problem even exists in the first place. Similarly, both anorexics and bulimics place all their achievements and successes as the result of their body, and for this reason are often depressed as they feel they are consistently failing to achieve the perfect body.

• The best method for preventing the progression of this disorder is early intervention by contacting your medical health professional and receiving psychotherapy.

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The ingestion and absorption of nutritious food is essential for life

Digestive system

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.

Defecation

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.

Food is utilized at a cellular level.

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). An 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