Nutrition and Digestion

Nutrients - carbohydrates, proteins, and fats.

The pyramid of nutrition  (Fig. 31.1, another idea, vegan) Movie Now


Carbohydrates and proteins contain an average of 4.1 calories per gram.

Fats have 9.3 calories per gram.

BMI (Body Mass Index) (
Fig. 31.2)



Essential Substances for Growth

Essential nutrients, such as essential amino acids.

Essential minerals

trace elements


Vitamins are essential organic nutrients that often act as cofactors for cellular enzymes. (Vitamins)

Digestion (movie)

Mechanical digestion

Chemical digestion.

Types of Digestive Systems

Gastrovascular cavity (Fig. 31.3) and feeding


One-way digestive tracts (Fig. 31.4)


Vertebrate Digestive Systems

tubular gastrointestinal tract and accessory organs. Ex: The human digestive system - (Fig. 31.5). The bird's digestive system (Fig. 31.7).

Carnivores have shorter intestines for their size than do herbivores, which have long, convoluted intestines as well as chambers where bacteria can digest cellulose. (
Fig. 31.15a) and (Fig. 31.15b).

Ruminant digestion. rumens (
Fig. 31.14) house bacteria where cellulose breakdown occurs.


Vitamin K.

The tubular gastrointestinal tract of vertebrates has four layers. (Fig. 31.6)



A double layer of muscle tissue.


The Mouth and Teeth

Teeth. (Fig. 31.8).

Teeth and diet


Children have 20 teeth and adults have 32 teeth. (Fig. 31.9).


Periodontal disease

Processing Food in the Mouth - the tongue helps mix the food with saliva from salivary glands.

Swallowing. (Fig. 31.10).

The soft palate is raised, closing off the nasal cavity, and muscles push the food past the larynx with its protective epiglottis, and into the esophagus, a muscular tube leading to the stomach.

Peristalsis. (Fig. 31.11).

Cardiac sphincter.

Structure and Function of the Stomach (Fig. 31.12)

Muscular sac

Hydrochloric acid and pepsin


For years, it was believed that ulcers were caused by excess stomach acid. Now it is known that they are caused by the bacterium Helicobacter pylori. Excess stomach acid can aggravate the ulcers, however. Movie

Pyloric sphincter.

Digestion and Absorption: The Small Intestine
Fig. 31.13)

Completes the chemical breakdown of food and is the major site of absorption of nutrients.





Accessory digestive organs


Pancreas (Fig. 31.16)

digestive enzymes

bicarbonate to neutralize the acidity




insulin Fig. 32.2

blood sugar

insulin receptors

incidence of diabetes


Concentration of Solids: The Large Intestine

The large intestine, or colon, compacts and stores feces, and reabsorbs water.

Feces are propelled toward the rectum, and they are eventually expelled through the anus.

The organs of the digestive tract (Fig. 31.17)

Problems with the appendix - appendicitis

Symptoms of appendicitis

     *Abdominal pain (located in the lower right side)

    * Fever

    * Reduced appetite

    * Nausea and vomiting

Treatment - appendectomy

Colorectal Cancer Risk Factors

* Polyps. Most -- perhaps all -- colorectal cancers develop in polyps. Polyps are benign
* Age. (over the age of 50)
* Family history. Close relatives of a person who has had colorectal cancer have a higher than average risk of developing the disease.
* Familial polyposis. An inherited condition in which hundreds of polyps develop and can become cancerous.
* Diet. Higher risk in people whose diet is
          high in fat
          low in fruits and vegetables
          low in high-fiber foods
* Ulcerative colitis. Causes inflammation of the lining of the colon increasing risk.

Colorectal Cancer Symptoms

The symptoms of colorectal cancer can be

* Fresh blood in the stools
* Lasting change in normal bowel habits (diarrhea or constipation)
* Unexplained weight loss
* Pain in the abdomen or rectum
* Straining feeling in the rectum

* anemia

Age is an important factor

Sometimes a cancer of the bowel can cause a blockage. The symptoms of this are

* Constipation
* Feeling bloated
* Griping pains in the abdomen

Colorectal Cancer Screening

Stool testing

* 'fecal occult blood test'
* a test for blood hidden in the stool

Examining the inside of the bowel

* sigmoidoscopy - examines only the last third of the colon

* colonoscopy - examines the entire colon

* Polyps - removed and biopsied - Removal

Elimination of nitrogenous wastes and osmoregulation (Balancing salts and water)





uric acid

Human excretory system  (Fig. 32.13a) and kidney  (Fig. 32.13b)

renal cortex

renal medulla

nephron (Fig. 32.13c).

Bowman's capsule


loop of Henle.

collecting duct.



urinary bladder


The nephron in review