Alimentary Canal Aka the gastrointestinal tract G I

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Alimentary Canal • Aka the gastrointestinal tract (G. I. tract) • The order is:

Alimentary Canal • Aka the gastrointestinal tract (G. I. tract) • The order is: • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Rectum • Anus

Ingestion and mastication

Ingestion and mastication

Mouth (aka Oral cavity) • Both physical (chewing food) and chemical digestion occur (salivary

Mouth (aka Oral cavity) • Both physical (chewing food) and chemical digestion occur (salivary amylase) • It contains multiple structures for breaking down food: • Teeth • Tongue • Salivary glands • Hard Palate • Soft Palate

Teeth • Primary teeth vs. secondary teeth

Teeth • Primary teeth vs. secondary teeth

Anatomy of a Tooth

Anatomy of a Tooth

Tooth • Enamel – White outer part of the tooth. Is mostly made of

Tooth • Enamel – White outer part of the tooth. Is mostly made of calcium phosphate, a rockhard mineral. • Dentin – has living cells, is porous, and is like bone (softer than enamel) • Pulp – the softer, living inner structure of teeth. Blood vessels and nerves run through the pulp.

Dental Caries (aka Cavities) • 500 species of bacteria inhabit the mouth. • Certain

Dental Caries (aka Cavities) • 500 species of bacteria inhabit the mouth. • Certain bacteria thrive on sugar, and produce lactic acid which destroys tooth enamel. • Streptococcus mutans

Teeth Questions • What are three types of teeth? What are they used for?

Teeth Questions • What are three types of teeth? What are they used for? • Why do Cavities Hurt? • Analyzing the teeth of animals is a good indication of their diet. Explain why. Sci. Show Videos • Why do we have baby teeth? • Why is flouride good for our teeth? • Why do we have to brush our teeth? List the two main reasons.

3 Types of teeth • Incisors: These teeth are excellent for biting and cutting

3 Types of teeth • Incisors: These teeth are excellent for biting and cutting food. • Canines (cuspids): Being pointed in shape they are used to tear or shred food. • Premolars and Molars: Both are flattened on the upper surfaces and are used for grinding and chewing food.

Root Canal • https: //www. youtube. com/watch? v=j. HHn 52 Kh. Bk. Q •

Root Canal • https: //www. youtube. com/watch? v=j. HHn 52 Kh. Bk. Q • https: //www. youtube. com/watch? v=YDs-848 -u-U

Tongue • Made up of groups of muscles that run in different directions. This

Tongue • Made up of groups of muscles that run in different directions. This gives the tongue its flexibility. • Mixes food with saliva to form a mass of wet food called a bolus. • Initiates swallowing by pushing bolus towards the pharynx

Tongue continued • The top layer of the tongue is covered with a layer

Tongue continued • The top layer of the tongue is covered with a layer of bumps called papillae • Papillae helps grip food and contains taste buds • People are born with ~10 000 taste buds, which decline as we age

Taste buds Can detect the following tastes: • Sweet • Salty • Sour •

Taste buds Can detect the following tastes: • Sweet • Salty • Sour • Bitter • Umami

Why is the tongue important in choosing the kinds of food you eat? Tastes

Why is the tongue important in choosing the kinds of food you eat? Tastes has a homeostatic function • Promotes the intake of nutritious foods that your body needs • Protects you body from possible dangers • Example: Natural poisons and spoiled foods tastes bitter

Do you taste different components of taste with different parts of your tongue? The

Do you taste different components of taste with different parts of your tongue? The “Taste Map”: All Wrong

Tongue Papillae Circumvallate papillae

Tongue Papillae Circumvallate papillae

Taste Test! • You will be tasting flavoured candies. Yummy • Catch! – You

Taste Test! • You will be tasting flavoured candies. Yummy • Catch! – You have to PLUG YOUR NOSE! • One student = facilitator, other = taster • Facilitator chooses 1 candy (don’t show the taster!), unwrap it while the taster has their eyes closed and put it in their hands. • 60 seconds (keep your nose plugged!) – describe sensations and try to determine the flavour of the candy. Guess again after the min is up. THEN unplug your nose. . . Switch roles and repeat. **Remember keep the flavour a secret until the end**

Taste • What is the difference between taste and flavour? • Does smell affect

Taste • What is the difference between taste and flavour? • Does smell affect taste? • If your sense of taste is impaired, it is possible your appetite might decrease. • What things might decrease your sense of taste? • Cigarettes, illness, medications, vitamin deficiencies

Babies response to sour taste • http: //www. dailymail. co. uk/news/article 2392574/Photographers-April-Maciborka. David-Wile-capture-toddlers-reactions-trying -lemon-time.

Babies response to sour taste • http: //www. dailymail. co. uk/news/article 2392574/Photographers-April-Maciborka. David-Wile-capture-toddlers-reactions-trying -lemon-time. html

Check Your Understanding! 1) What is the tongue? What function does it perform? 2)

Check Your Understanding! 1) What is the tongue? What function does it perform? 2) How many different tastes can the tongue detect? What are the tastes? 3) What kind of homeostatic function does your tongue serve? Explain.

Salivary Glands • There are three types of salivary glands: 1. Parotid Glands 2.

Salivary Glands • There are three types of salivary glands: 1. Parotid Glands 2. Submandibular Glands 3. Sublingual Glands

Salivary Glands continued • Serous cells produce amylase – splits starch and glycogen into

Salivary Glands continued • Serous cells produce amylase – splits starch and glycogen into disaccharides

Salivary Glands continued • Mucous cells produce mucus – lubrication during swallowing • Saliva

Salivary Glands continued • Mucous cells produce mucus – lubrication during swallowing • Saliva is 99% water, the rest is mucus, salts, and enzymes • The water in saliva moistens and dissolves particles of food, aiding chemical digestion, the ability to taste, and the chewing process

Exocrine glands • Are glands that produce and secrete substances onto an epithelial surface

Exocrine glands • Are glands that produce and secrete substances onto an epithelial surface by way of a duct • For example: Salivary Glands

Swollen parotid gland in child with viral mumps. This virus can also infect the

Swollen parotid gland in child with viral mumps. This virus can also infect the testes.

Parasympathetic innervation stimulates salivary gland secretion (anticipation of tasty food). Sympathetic stimulation inhibits normal

Parasympathetic innervation stimulates salivary gland secretion (anticipation of tasty food). Sympathetic stimulation inhibits normal secretion, which is why people who are frightened experience the sensation of a dry mouth.

Check Your Understanding! • Describe the chemical digestion that occurs in the mouth •

Check Your Understanding! • Describe the chemical digestion that occurs in the mouth • Mucus is found in saliva. What might its function be?

Movement!!

Movement!!

Swallowing • Voluntary • Tongue pushes bolus to back of throat (Pharynx) • Soft

Swallowing • Voluntary • Tongue pushes bolus to back of throat (Pharynx) • Soft palate closes off nasal passage • Epiglottis closes off the trachea and food travels down esophagus

Pharynx • The junction between nasal and oral cavity, part of the throat

Pharynx • The junction between nasal and oral cavity, part of the throat

 • Can you drink upside down?

• Can you drink upside down?

Can you drink upside down? Questions: 1. Is gravity needed to make fluids come

Can you drink upside down? Questions: 1. Is gravity needed to make fluids come down the esophagus? 2. Can we drink while we stand on our head? 3. How does food go down the esophagus into the stomach? 4. Why did the fluid not flow out of the mouth when drinking upside down? 5. What is the muscle action called, which pushes food into the stomach?

Esophagus • Esophagus is made of smooth muscle that becomes stretched to help food

Esophagus • Esophagus is made of smooth muscle that becomes stretched to help food bolus move along. • Inside is covered in a thick lining of mucus • Causes a wavelike contraction called PERISTALSIS. • Reverse peristalsis = Vomiting

The wall of the esophagus contains both circular and longitudinal muscle.

The wall of the esophagus contains both circular and longitudinal muscle.

Movement cont. • Smooth muscle contractions also move food through the rest of the

Movement cont. • Smooth muscle contractions also move food through the rest of the digestive tract.

Digestion / Absorption

Digestion / Absorption

Sphincter • A sphincter is a ring of muscle that controls the passage of

Sphincter • A sphincter is a ring of muscle that controls the passage of material. Relaxed = open, Contracted = closed • At the junction of esophagus and stomach is the cardiac sphincter (AKA Lower Esophageal Sphincter). Stops stomach contents from going into esophagus

 • At the junction of stomach and duodenum is the pyloric sphincter. Regulates

• At the junction of stomach and duodenum is the pyloric sphincter. Regulates movement of stomach contents from stomach small intestine.

Draw This!

Draw This!

Heart Burn • Caused by a cardiac sphincter that doesn’t tighten as it should

Heart Burn • Caused by a cardiac sphincter that doesn’t tighten as it should stomach acid into esophagus • Often happens when too much food in the stomach (overeating) or to much pressure on the stomach (obesity, pregnancy) • Certain foods act as a trigger (relaxes the sphincter or causes more acid production smoking causes both!)

The Stomach • Site of initial protein digestion and food storage. • Smooth muscle

The Stomach • Site of initial protein digestion and food storage. • Smooth muscle contractions cause ingested food to be crushed, ground, and mixed, liquefying it to form Chyme

Gastric Pits

Gastric Pits

Gastric Pits • Stomach contains GASTRIC PITS that have GLANDS and MUCUS cells. Glands

Gastric Pits • Stomach contains GASTRIC PITS that have GLANDS and MUCUS cells. Glands contain: • Parietal cells – secrete HCl (hydrochloric acid) • Chief cells – secrete pepsinogen, the zymogen (inactive) form of the digestive enzyme pepsin. (Pepsinogen Pepsin under low p. H)

 • Pepsin breaks down proteins into short amino acid chains

• Pepsin breaks down proteins into short amino acid chains

 • G cells – secretes gastrin, a hormone. Gastrin stimulates the secretion of

• G cells – secretes gastrin, a hormone. Gastrin stimulates the secretion of HCl and aids in stomach motility. • Gastrin is released in response to stomach stretching or the presence of proteins in the stomach. It is inhibited by HCl in the stomach. What kind of feedback is this? ?

The J-shaped stomach stores food (the semi-digested mass is called chyme), initiates the digestion

The J-shaped stomach stores food (the semi-digested mass is called chyme), initiates the digestion of proteins, has only minimal absorption, and moves materials on to the small intestine.

Absorption • Some water, specific vitamins and alcohol

Absorption • Some water, specific vitamins and alcohol

Stomach Composition • The stomach has four layers that surrounds the space called the

Stomach Composition • The stomach has four layers that surrounds the space called the lumen. 1) 2) 3) 4) Mucosa Submucosa Muscle layer Serosa • The stomach has folded membranes on the inside called Rugae allows stomach to expand

Why doesn’t the stomach digest itself? • Mucous cells in the gastric pits secrete

Why doesn’t the stomach digest itself? • Mucous cells in the gastric pits secrete a thick layer of mucus which protects the walls of the stomach • also secrete bicarbonate solution which neutralizes stomach acid (acid base reaction)

Peptic Ulcers

Peptic Ulcers

Peptic Ulcer • Most commonly caused by bacterial infection Helicobacter pylori • NSAIDS (non-steroidal

Peptic Ulcer • Most commonly caused by bacterial infection Helicobacter pylori • NSAIDS (non-steroidal anti-inflammatory drugs) aspirin and IBProfen • Smoking • Alcohol • Genetics

A Very Famous Stomach! • Alexis St. Martin, 1822 • https: //www. youtube. com/watch?

A Very Famous Stomach! • Alexis St. Martin, 1822 • https: //www. youtube. com/watch? v=pqgc EIa. XGME

Mechanical vs Chemical recap Mechanical – churning of stomach Chemical : • HCl denatured

Mechanical vs Chemical recap Mechanical – churning of stomach Chemical : • HCl denatured proteins and kills ingested bacteria • Pepsin begins protein digestion

Check your understanding • What is the function of the 2 sphincters in the

Check your understanding • What is the function of the 2 sphincters in the stomach • What role does each cell in the gastric pit play? • Describe the chemical digestion that occurs in the stomach