Nutrients - carbohydrates, proteins, and fats.
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
such as essential amino
Vitamins are essential organic nutrients that often act as cofactors for cellular enzymes. (Vitamins)
Types of Digestive Systems
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.
The tubular gastrointestinal tract of vertebrates has four layers. (Fig. 31.6)
A double layer of muscle tissue.
The Mouth and Teeth
Children have 20 teeth and adults have 32 teeth. (Fig. 31.9).
Processing Food in the Mouth - the tongue helps mix the food with saliva from salivary glands.
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).
Structure and Function of the Stomach (Fig. 31.12)
Hydrochloric acid and pepsin
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
Digestion and Absorption: The Small Intestine (Fig. 31.13)
Completes the chemical breakdown
of food and is the major site of absorption
Accessory digestive organs
Pancreas (Fig. 31.16)
bicarbonate to neutralize
insulin Fig. 32.2
incidence of diabetes
Concentration of Solids: The Large Intestine
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)
Symptoms of appendicitis
*Abdominal pain (located in the lower right side)
* 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
an important factor
Sometimes a cancer of the bowel can cause a blockage. The symptoms of this are
* Feeling bloated
* Griping pains in the abdomen
Colorectal Cancer Screening
* '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
* colonoscopy - examines the entire colon
Elimination of nitrogenous wastes and osmoregulation (Balancing salts and water)
nephron (Fig. 32.13c).
loop of Henle.