Laboratory 14 - The Digestive System (Pt 1)

The digestive system can be divided into two components. What are they?

- The digestive tract.
- Accessory organs.

What is the digestive tract?

A hallow tube extending from mouth to anus.

What are accessory organs?

They aid in digestion but food doesn't pass through them.

What do the accessory organs include? (6)

- Teeth
- Tongue
- Salivary glands
- Liver
- Gall bladder
- Pancreas

The mouth has been specialized for what?

Ingestion and the mechanical processing of food.

The teeth are located in the mouth and are surrounded by a delicate mucosa called what?

Gingiva (or gums).

The roof of the mouth is formed by what?

The hard palate (anteriorly) and the soft palate (posteriorly).

The mouth cavity is filled by what accessory organ?

The tongue.

The tongue functions in what three things?

Food manipulation, taste, and speech.

What nerves innervate the tongue?

- Facial nerve (VII)
- Glossopharyngeal nerve (IX)
- Vagus nerve (X)

What is mastication? This is done by what?

Chewing. Performed by teeth.

What are the different types of teeth?

Incisors, canines, premolars, molars.

What shape are incisors and what do they do?

Chisel-shaped. They are used for cutting and shearing food.

What shape are canines and what do they do?

Pointy (aka as cuspids), with a single cusp. They are used for shredding food.

What shape are premolars and what do they do?

Bicuspid (2 cusps). Adapted for crushing and cracking food.

What shape are molars and what do they do?

Tricuspid (3+ cusps). Adapted for grinding food into fine pieces for chemical digestion.

Humans and all other mammals have two sets of teeth in their lifetime. What are the two stages called?

- Deciduous (primary/baby teeth)
- Permanent (secondary/adult teeth)

When do teeth start appearing in babies?

Around six months.

When is the deciduous teeth completed?

Around age six.

Deciduous teeth are a total of \__ teeth.

20

What is a dental formula?

The way teeth are described by name and number. It represents ONE top half (top number) and ONE bottom half (bottom number) of the jaw.

What is an infant's dental formula?

I 2/2, C 1/1, P 0/0, M 2/2

When does permanent teeth begin pushing out on deciduous teeth?

Around age six until 11 or 12.

In the adult, how many teeth are in each jaw?

16.

In the adult, how many teeth are there in total?

32.

What is an adult's dental formula?

I 2/2, C 1/1, P 2/2, M 3/3

All teeth are constructed on a basic plan of two principal parts. What are they?

- The crown (visible)
- The root (in alveolus - the bony socket of the maxilla or mandible)

Where is the enamel of a tooth?

Where is the crown of a tooth?

Where is the dentin of a tooth?

Where is the alveolar bone (bony socket) of a tooth?

(K)

Where is the root canal of a tooth?

Where is the cementum if a tooth?

Where is the gingiva of a tooth?

Where is the root of a tooth?

Where is the periodontal membrane of a tooth?

(I)

Where is the pulp cavity of a tooth?

The salivary glands are considered accessory organs in the mouth. How many are there?

Three.

What are the three salivary glands?

- Parotid glands
- Sublingual glands
- Submandibular glands

Describe the partoid gland.

- Largest of the three glands
- Irregular shape
- Overlaps the masseter muscle

Describe the sublingual gland.

- Smallest of the three glands
- Are deep and anterior to the submandibular glands

Describe the submandibular gland.

- Inferior to the parotid gland
- Situated along the inner surfaces of the mandible

All the salivary glands does what?

They secrete saliva.

What are the functions of saliva? (3)

- Lubrication of the mouth
- Moistening food
- Dissolving chemicals so they can be tasted.

Saliva contains what enzyme that is important in the breakdown of carbohydrates into simple sugars?

Salivary amylase.

After the mouth, food goes where to get into the esophagus?

Into the oropharnyx and then the laryngopharynx.

Is the nasopharynx part of the digestive tract?

No.

Food chewed in the mouth is called what?

Bolus.

What is the esophagus?

A muscular tube that connects the mouth to the stomach.

How is food prevented from going into the trachea?

While swallowing, the epiglottis folds over and seals the trachea and directs food into the esophagus.

What is choking caused by?

Food accidentally making its way into the trachea.

What is the stomach?

A large, crescent-shaped organ that is the site of the beginning of protein digestion.

The stomach has an extra layer of smooth muscle. Why?

It helps to protect the stomach by the chemical digestion that occurs within and it also helps in the moving the the stomach to churn food.

The stomach has also act as what?

A temporary storage site for food.

Food in the stomach mixed with stomach acid is called what?

Chyme.

The small intestines is the \_______ digestive organ of the body.

primary

Where is the chemical digestion of food completed?

In the small intestines.

Where does the absorption of nutrients occur?

In the small intestine.

What are the three parts of the small intestine from beginning to end?

- Duodenum
- Jejunum
- Ileum

The duodenum recieves partially digested food and secretions from what?

The pancreas, the liver, and the gallbladder.

Where is the large intestine?

Between the Ileum and the anus.

What is the major function of the large intestine?

Water absorption.

What is the first part of the large intestine?

The cecum.

What is attached to the cecum?

The vermiform appendix.

From the cecum, what follows?

The ascending colon.

The ascending colon turns into what?

The transverse colon.

The transverse colon turns into what?

The descending colon.

The descending colon forms and s-shape at the end, called what?

The sigmoid colon.

The sigmoid colon continues to what?

The rectum.

The rectum leads to what?

The anus.

There are three accessory organs found in the abdominal cavity. What are they?

- Liver
- Gallbladder
- Pancreas

Where is the liver located?

In the upper right quadrant, immediately beneath the diaphragm.

What is the digestive function of the liver?

The production and secretion of bile.

The liver is divided into how many lobes?

Two.

Lobes of the liver is made out of what?

Lobules.

Describe the shape of lobules.

Roughly hexagonal shape, consisting of plates of liver cells or hepatocytes. These radiate from a central vein.

Hepatocytes manufacture bile, which does what?

It is a fat emulsifier which is secreted into tiny channels, bile canaliculi.

At the corners of each liver lobule is what?

A portal triad.

What is the portal triad?

The hepatic artery, portal vein, and bile duct.

Blood from both hepatic portal vein and hepatic artery flow from the triad region into what?

The liver sinosoids. (B)

What are liver sinosoids?

Capillary channels located between the hepatocytes.

From the liver, blood goes where?

Empties into the central vein, eventually entering the hepatic veins which carry blood to the inferior vena cava.

What is the gallbladder?

A green coloured muscular sac attached to the ventral surface of the liver.

Bile produced in the liver is is stored and concentrated where?

The gallbladder.

What is the pancreas?

A large organ lying in between the stomach and duodenum.

The pancreas is 98% what?

Endocrine glands.

Endocrines are ductless glands consisting of groups of cells called what?

Islets of Langerhans, which releases hormones into the blood.

Where is the spleen?

Is the spleen part of the digestive system?

No.

The serous membrane that lines the abdominopelvic cavity and covers most of the abdominal organs called what?

The peritoneum.

The peritoneum can be divided into what two parts?

The visceral peritoneum which covers the external surface of most of the digestive organs and the parietal peritoneum, lining the walls of the abdominopelvic cavity.

What is the function of the fluid produced by the peritoneum?

It helps to prevent friction between organs.

What are mesenteries?

Folds of peritoneum that hold digestive organs in place. They contain blood vessels, lymphatic vessels, and nerves.

What is the omentum?

A mesentery that hangs free in the abdominal cavity or connects organs to each other.

Where is the greater omentum?

It is a double-walled peritoneal sac that extends from the greater curvature of the stomach, over the small and large intestines.

Attached to the left side of the greater omentum is what?

The spleen.

Where is the lesser omentum?

Between liver and stomach.

What is the falciform ligament?

It connects liver to anterior abdominal wall.

What is the mesentery that connects the different parts of the small intestine to each other?

Mesentery proper.

How many layers compose the wall of the digestive tract from the esophagus and extending to the anal canal?

Four.