Topic 6.1 - Human Physiology Flashcards Preview

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What are two major groups of organs which comprise the human digestive system?

Alimentary canal
Accessory organs


What is the alimentary canal?

The alimentary canal consists of organs that that passes food through them. Eg, esophagus, stomach, small & large intestine.


What are accessory organs and what does it do?

The accessory organs aid in digestion but do not actually transfer food (salivary glands, pancreas, liver, gall bladder)


What's the Oesophagus and its function?

A hollow tube connecting the oral cavity to the stomach (separated from the trachea by the epiglottis)

• Food is mixed with saliva and then is moved in a bolus via the action of peristalsis


What's the Stomach and its function?

• A temporary storage tank where food is mixed by churning and protein digestion begins

• It is lined by gastric pits that release digestive juices, which create an acidic environment (pH ~2)


What's the small intestine and its function?

• A long, highly folded tube where usable food substances (nutrients) are absorbed

• Consists of three sections – the duodenum, jejunum, and ileum


What's the large intestine and its function?

• The final section of the alimentary canal, where water and dissolved minerals (i.e. ions) are absorbed

• Consists of the ascending/transverse/descending/sigmoidal colon, as well as the rectum


What's the Salivary Gland and its function?

• Release saliva to moisten food and contains enzymes (e.g. amylase) to initiate starch breakdown

• Salivary glands include the parotid gland, submandibular gland, and sublingual gland


What's the pancreas and its function?

• Produces a broad spectrum of enzymes that are released into the small intestine via the duodenum

• Also secretes certain hormones (insulin, glucagon), which regulate blood sugar concentrations


What's the liver and its function?

• Takes the raw materials absorbed by the small intestine and uses them to make key chemicals

• Its role includes detoxification, storage, metabolism, bile production, and hemoglobin breakdown


What's the gall bladder and its function?

• The gall bladder stores the bile produced by the liver (bile salts are used to emulsify fats)

• Bile stored in the gall bladder is released into the small intestine via the common bile duct


Food can be digested by a combination of two methods, what are they?

Mechanical digestion and chemical digestion?


How does mechanical digestion work?

Food is physically broken down into smaller fragments via the acts of chewing (mouth), churning (stomach) and segmentation (small intestine)


2 examples of mechanical digestion:

Chewing (mouth)
Churning (stomach)


2 examples of how food is transported:



What is peristalsis?

- Peristalsis is the principal mechanism of movement in the esophagus, although it also occurs in both the stomach and gut
- Continuous segments of longitudinal smooth-muscle rhythmically contract and relax
- Food is moved unidirectionally along the alimentary canal in a caudal direction (mouth to anus)


What is segmentation?

- Segmentation involves the contraction and relaxation of non-adjacent segments of circular smooth muscle in the intestines
- Segmentation contractions move chyme in both directions, allowing for a greater mixing of food with digestive juices
- While segmentation helps to physically digest food particles, its bidirectional propulsion of chyme can slow overall movement


How does chemical digestion work?

In chemical digestion, food is broken down by the action of chemical agents (such as enzymes, acids, and bile)


What are carbohydrates?

- Carbohydrate digestion begins in the mouth with the release of amylase from the salivary glands (amylase = starch digestion)
- Amylase is also secreted by the pancreas in order to continue carbohydrate digestion within the small intestine
- Enzymes for disaccharide hydrolysis are often immobilized on the epithelial lining of the small intestine, near channel proteins
- Humans do not possess an enzyme capable of digesting cellulose (cellulose) and hence it passes through the body undigested


What are proteins?

- Protein digestion begins in the stomach with the release of proteases that function optimally in an acidic pH (e.g. pepsin = pH 2)
- Smaller polypeptide chains enter the small intestine where they are broken down by endopeptidases released by the pancreas
- These endopeptidases work optimally in neutral environments (pH ~ 7) as the pancreas neutralizes the acids in the intestine


What are lipids?

- Lipid breakdown occurs in the intestines, beginning with emulsification of fat globules by bile released from the gall bladder
- The smaller fat droplets are then digested by lipases released from the pancreas


What are the nucleic acids?

- The pancreas also releases nucleases which digest nucleic acids (DNA, RNA) into smaller nucleosides


Why does the human intestine?

The human intestines function to absorb the products of digestion and have specialized structures to fulfill this function

The small intestine absorbs usable food substances (i.e. nutrients – monosaccharides, amino acids, fatty acids, vitamins, etc.)

The large intestine absorbs water and dissolved minerals (i.e. ions) from the indigestible food residues


What are the 4 main tissue layers of the small intestine?

- Serosa – a protective outer covering composed of a layer of cells reinforced by fibrous connective tissue
- Muscle layer – an outer layer of longitudinal muscle (peristalsis) and an inner layer of circular muscle (segmentation)
- Submucosa – composed of connective tissue separating the muscle layer from the innermost mucosa
- Mucosa – a highly folded inner layer which absorbs material through its surface epithelium from the intestinal lumen


What does the small intestine absorb?

The small intestine absorbs usable food substances (i.e. nutrients – monosaccharides, amino acids, fatty acids, vitamins, etc.)


What does the large intestine absorb?

The large intestine absorbs water and dissolved minerals (i.e. ions) from the indigestible food residues


What does the inner epithelial lining of the intestine consist of?



What are the 6 key features of villi? (MRSLIM)

Rich blood supply
Single-layer epithelium
Intestinal glands
Membrane proteins


Structure of Villus Epithelium?

Pinocytotic Vesicles
Tight Junctions


What mus happen during absorption?

Digested food monomers must pass from the lumen into the epithelial lining of the small intestine