BIOLOGY 151 MODULE 3 SUMMARY NOTES PORTAGE

BIOLOGY 151 MODULE 3 SUMMARY NOTES ( PORTAGE

LEARNING)

Human digestive organs can be divided into two main groups:

• The alimentary canal
• The accessory digestive organs

The alimentary canal – also called gastrointestinal tract.

• A continuous muscular digestive tube beginning in the oral cavity.
• Opens at both ends, winding its way through the body cavity
• Composed of the mouth (oral cavity), pharynx (throat), esophagus, stomach, small

intestine, large intestine, and anus The accessory digestive organs

• Teeth, tongue, gall bladder, salivary glands, liver, and pancreas

(see Figure 3.1 and Figure 3.4).

Figure 3.1 Upper alimentary canal (oral cavity and pharynx highlighted in blue)

Figure 3.2 Anterior view of lower alimentary canal in context with accessory organs (pancreas and gall bladder). The stomach is highlighted in blue. 1 / 3

Figure 3.3 Alimentary canal from the esophagus to the anus, with cross section view of the layers found in the alimentary canal

Figure 3.4 Anterior view of the accessory organs: Liver, pancreas, and gall bladder. The stomach is removed to view the pancreas (which lies posterior to the stomach).

Mouth - Beginning of the gastrointestinal tract. Made up of the following:

• Lips form the opening
• Tongue forms the floor
• The cheeks form the walls
• The hard and soft palates form the roof
• Uvula forms the posterior border
• Uvula – process that hangs inferiorly from its attachment to the soft palate
• Tongue – a muscle, attaches to other structures so it can contract for movement

▪ Attachments: hyoid bone, the mandible, and the lingual frenulum

• Lingual frenulum – vertical mucous membrane by which the body of the tongue is attached to the floor of the mouth 2 / 3

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• Figure 3.5 Midsagittal view of the oral cavity to the trachea

Digestive system – begins when food enters the mouth

• Mechanically, food is chewed by the teeth in the mouth, which is a process known as

mastication

• The food is mixed and moistened with saliva from the salivary glands.
• Salivary glands contain enzymes (amylase) that begin the process of chemical

digestion by breaking down starches Teeth –

• 32 teeth in the human mouth
• Upper arch of teeth is located within the maxilla
• The movable, lower mandible contains the lower arch of the teeth
• 4 different types of teeth to accommodate both a vegetable and meat diet
• One-half of each jaw has two chisel-shaped incisors for biting, one pointed canine for

tearing, two increasingly flat pre-molars for grinding, and three flat molars for crushing.

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• Figure 3.6 Upper arch of teeth, right side teeth labeled
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