Digestive System - Human Systems - Lecture Slides, Slides of Human Biology

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The Digestive System

This lesson brought to you courtesy of

Human Anatomy and Physiology 4 th^ Edition by Elaine Marieb Don’t write the red writing.

Digestive Processes (Functions)

• Ingestion – Taking food in.
• Propulsion – The process that moves food through the digestive tract (also known the alimentary canal). The movement that does this is called peristalsis.
• Mechanical Digestion – Physical processing of food that makes digestion by enzymes easier.
• Chemical Digestion – catabolic (breaking down) steps that involve enzymes.

Smooth Muscle Movements

• Peristalsis
  • wave of smooth muscle contractions that move food down the alimentary canal
• Reverse peristalsis
  • A more technical way of saying: vomiting, throwing up, chucking, technicolour yawning, spewing, revisiting lunch or blowing chunks – sorry for stretching the point, I just had to get that out my system….which, incidentally, is a really bad way to apologize for throwing up on someone

Mouth and related organs

• What processes does the mouth perform?
• Teeth
• Tongue
• Cheeks
• Hard Palate
• Soft palate
  • uvula

Epiglottis

• Is a flap that covers the trachea when we swallow and prevents food from blocking our airway.

Pancreatic and Intestinal

enzymes

• As a general rule pancreatic enzymes break long chain molecules smaller chains or MUCH smaller chains and the intestinal enzyme break them up into their basic components e.g. proteins into amino acids.

Stomach function

• It breaks proteins down into large polypeptides.
• Mechanical Digestion of food
• The stomach acid helps to kill off most bacteria and well as denaturing the protein.
• May detect if the food has gone off/is toxic and induce vomit reflex.

Small Intestine

• The tube that exits the stomach.
• It has 3 parts: the duodenum, jejunum and ileum

The jejunum and the ileum

• Major sites for absorption of nutrients are - Jejunum 2.5 m - Ileum 3.6 m
• Heavy modified to increase surface area.

Surface Area Increasing

Structures

• There are circular folds ( plicae cirulares in Latin) in the small in intestine that are about 1cm deep.
• On the circular folds are 1mm high finger like projections called villi (singular villus). Each of these contains blood and lymph vessels to absorb nutrients.
• Each cover each villus has mircovilli on there absorptive cells , these are also covered in enzymes called Brush Border Enzymes that break down nutrients. Docsity.com

Rectum and Anus

• The Rectum is the final part of the digestive tract.
• The anus is the opening at the end of the digestive tract. It is surrounded by a circular muscle called the anal sphincter which allows you to refrain from defecation until it is convenient.