1
Q
Alimentary Canal def
A
refers to the one-way digestive tract running from the mouth to the anus
2
Q
Digestive System def
A
refers to the digestive tract and organs associated with digestion
3
Q
Ingestion def
A
process of putting food into the body
4
Q
Digestion def
A
process of breaking food into molecules small enough for body’s cells to absorb
5
Q
Egestion def
A
removal of undigested material from the anus
6
Q
Has undigested food ever been in the body?
A
NO! It’s never been in the body’s cells!
7
Q
Excretion def
A
process of removing substances from the body that was once part of living tissue (eg. pee or sweat)
8
Q
Mechanical Digestion def
A
involves shredding, grounding, or shaking food to break it down by physical means
9
Q
Where does physical digestion occur? And how do you know it is physical?
A
- Mouth and stomach
- No enzymes therefore no bonds being broken
10
Q
Chemical Digestion def
A
involves the breakdown of smaller food particles with the help of digestive enzymes
11
Q
Mouth: teeth
A
carries out mechanical digestion by smashing food MAKING IT EASIER TO SWALLOW
12
Q
Mouth: saliva (composition, names of salivary glands, volume of saliva a day, function)
A
- 99% water, ions, mucous, enzymes
- Produced by 3 pairs of salivary glands: parotid, submaxillary, and sublingual which secrete approx 1 L of saliva a day
- Carries out chemical digestion as the digestive enzyme amylase begins the BREAKDOWN OF CARBOHYDRATES
- Softens and moistens food during chewing which PREVENTS ABRASIONS inside the mouth
13
Q
Mouth: tongue
A
- Helps MANIPULATE the food while chewing into a ball called a bolus
- PUSHES BOLUS into the pharynx
14
Q
Pharynx aka Throat (leads to what?, function, essential structure)
A
- Leads to esophagus and trachea
- Voluntarily contracting muscles to PUSH FOOD into esophagus
- Trachea moves up so that entrance is sealed off by epiglottis to prevent food from entering trachea (or else you will die)
15
Q
Esophagus: general function, length
A
- Approx 25 cm long and 2 cm wide
- Conducts food from pharynx to the stomach
16
Q
Esophagus: Mucosa (structure and function)
A
- Inner layer
- Contains glands supported by connective tissue
- SECRETES MUCOUS without enzymes which help transport the food
- Connective tissue HOLDS ORGANS IN PLACE
17
Q
Esophagus: Submucosa (structure)
A
Contains blood vessels, nerves, and connective tissue
18
Q
Esophagus: Muscularis (structure and function)
A
- Contains circular (inner) and longitudinal (outer) muscles which works against gravity to PERFORM PERISTALSIS
- Upper ⅓ has straited muscle (voluntary) so if you are sick, you will vomit
- Lower ⅔ has smooth muscle (involuntary)
19
Q
Peristalsis: def
A
wave-like muscular contraction which pushes bolus from upper to lower end of esophagus OR chyme through intestines
20
Q
Stomach: (volume of food, time to empty, new name of food, backflow, functions)
A
- Holds 1.5 L of food
- Takes about 2-6 hours after a meal for the stomach to empty
- When the food leaves the stomach, it is referred to as chyme which is a semi-liquid, partially digested meal
- If backflow occurs into the esophagus, heartburn will occur
- In general, the stomach functions to STORE FOOD and PERFORM mechanical and chemical digestion
21
Q
Stomach: 4 layers
A
- Longitudinal muscle (outermost layer)
- Circular muscle
- Oblique muscle
- Rugae (innermost wall)
- Accordian like folds, elastic
- Allow stomach to EXPAND and CONTRACT
- Contain gastric pits which consist of gastric glands which produce gastric juice
22
Q
Stomach: gastric juice (pH, volume, components and their function)
A
- pH of 2
- 3L of gastric juice is secreted each day which contain;
- Hydrochloric acid
- Chemically BREAKS down food particles
- ACTIVATES enzymes
- KILLS bacteria in food - Pepsinogen
- Gets converted into pepsin which DIGESTS PROTEIN - Mucous
- Lines stomach and PROTECTS it from HCl - Rennin
- SLOWS down fat so it can be digested
23
Q
Stomach: sphincters (name, structure, function, closed or nah)
A
- Cardiac Sphincter
- Ring of muscle around top of stomach
- Opens with every wave of peristalsis to ALLOW BOLUS OF FOOD to enter the stomach
- Mostly closed - Pyloric Sphincter
- Ring of muscle around bottom of stomach
- Helps REGULATE PASSAGE of chyme into duodenum of small intestine
- Mostly closed
24
Q
Small Intestine: length + why
A
- Largest component of digestive tract (6m long)
- To ensure all NUTRIENTS ARE ABSORBED to get the most energy because energy is scarce!
25
Small Intestine: general functions
1. Finishes digestion by breaking food into its simplest form
- Proteins into amino acids
- Carbohydrates into monosaccharides
- Fats or lipids into 1 glycerol, 3 fatty acids
2. Absorbs products of digestion into body
- 80% of absorption occurs here, the other 20% occurs in stomach and large intestine
26
Small Intestine: what happens after food passes through absorptive cells?
- Water soluble nutrients (proteins, carbs) flow into blood capillaries of the villi to transport to liver to process and then to all body’s cells
- Fatty products of digestion (fat) are absorbed into lacteal which are tiny lymphatic vesicles in the villi that connect to hlymphatic system
27
Small Intestine: regions
Region #1: Duodenum
- 25 cm long
- First part
Region #2: Jejunum
- 2.5 m long
- Middle part
Region #3: Illeum
- 3.5 m long
- Last part
28
Small Intestine: layer 1
Serosa/Mesentery
- Outermost layer
- Sheet of connective tissue
- PREVENTS TANGLING of small intestine
29
Small Intestine: layer 2
Circular Muscle
| - For PERISTALSIS
30
Small Intestine: layer 3
Longitudinal Muscle
| - For PERISTALSIS
31
Small Intestine: layer 4
Inner Mucosa Layer
- Consists of many folds that consists of many villi: finger-like projections which face the lumen (space inside) of the small intestine
- Increases surface area to ABSORBS MORE NUTRIENTS for energy because energy is scarce
- Epithelium (absorptive cells) line the surface of the villi
- Each absorptive cell contains many microvilli
- ALWAYS IN CONTACT WITH FOOD
32
Pancreas: location + function
- Right beside duodenum of small intestine
| - Secretes pancreatic juice containing digestive enzymes into duodenum of the small intestine
33
Pancreas: pancreatic juice
- Basic/alkaline to NEUTRALIZE chyme as it enters duodenum
- Digestive enzymes include tripsinogen and pepsinogen (digest protein into amino acids), amylases (digest carbohydrates into monosaccarides), and lipases (digest lipids into 1 glycerol and 3 fatty acids)
34
Liver: function, def of juice it excretes, def of process
- Secretes bile
Bile: doesn’t contain digestive enzymes but contains bile salts which emulsifies fat
Emulsification: process in which large droplets of fat are broken into tiny droplets by a physical reaction TO SPEED UP FAT ABSORPTION
35
Gall Bladder: structure + function
- Bag
| - Stores bile until needed
36
Large Intestine aka colon: length, general functions
- Approx 1.5m long
- COMPLETES RE-ABSORPTION OF WATER
- 90% of water is reabsorbed by the intestines which causes feces to become solid
Water is also scarce
- FORMS CERTAIN VITAMINS
- Colon contains large flora of bacteria which feed off organic matter of feces, producing vitamins (vitamin K) and gases (methane)
- COMPLETES NUTRIENT ABSORPTION
- Salts and some vitamins are reabsorbed in the colon
- ELIMINATION OF FECES
37
Large Intestine aka colon: 7 structures
Caecum
- Chamber in which chyme passes from small into large intestine
Ascending Colon
- Goes up the right side of abdominal cavity
Transverse Colon
- Goes across the middle of the abdomen
Descending Colon
- Goes down the left side of the abdominal cavity
Sigmoid Colon
- Leads descending portion of the colon to the rectum
Rectum
- Stores feces until it can be egested
Anus
- Actual site of elimination
38
Feces at rectum composition
- Feces is 25% water and 75% solid at this point
- The solid part consists of 30% bacteria, 30% undigested roughage (fiber) which acts like scrapper for colon, 20% fats, and 15% inorganic matter
39
Esophageal Sphincter (function & structure)
- Ring of muscle
- Entrance to stomach
- PREVENTS ACIDIC CONTENTS of stomach from backing up into esophagus; relaxes to allow bolus of food to enter stomach
40
System
- Smell/sight of food triggers salivary glands to secrete saliva that contains amylase to break down water-soluble particles
- Teeth performs mechanical digestion which makes it easier to swallow and exposes more surface area of food to saliva
- Tongue molds food into a bolus and when swallowed, enters esophagus to begin passage to stomach via peristalsis
- Food enters stomach via esophageal sphincter and undergoes chemical and mechanical digestion that forms chyme
- Stomach nerves will release partially digested food into small intestine when small intestine is empty
- Food is pushed via peristalsis into duodenum
- Duodenum receives secretions from the pancreas and the gall bladder which help break down food
- Jejunum breaks down remaining proteins and carbohydrates
- Illeum finishing absorbing nutrients and pushes remaining undigested material into large intestine
- Large intestine reabsorbs water
- Bacteria in colon break down undigested matter further
- Leftover solid waste is egested
41
Macromolecule: def
A very large molecule made up of smaller molecules linked together; nutrients that our bodies need to provide energy, regulate cellular activites, and to build tissues
42
Carbohydrates: function & types
Provide quick energy for use by cells
1. Monosaacharides
- Molecules with 3-7 C atoms (2 atoms of H and 1 atom of O for each atom of C)
- Eg. glucose, fructose
2. Disaacharides
- Made up of 2 monosaacharides
- Eg. sucrose, maltose, lactose
3. Polysaccharides
- Made up of many monosaacharides
- Eg. starch, cellulose, glycogen
43
Carbohydrates: digestion
MOUTH (polysaacharides → “salivary amylase” → disaccharides)
SMALL INTESTINE (polysaacharides & disaccharides → “carbohydrases” → monosaccharides)
44
Lipids: function & structure
Stores energy reserves for later use, cushions internal organs
- Insoluble in water
- 1 molecule of glycerol (3 C atoms) attached to fatty acid chain (lots of C and H)
45
Lipids: digestion
SMALL INTESTINE (fat droplets → “bile” → emulsified fat droplets → “lipases” → 1 glycerol & 3 fatty acids)
46
Proteins: function & structure
- Aids in muscle movements, speed up chemical reactions, provide immunity, transport ions, provide support for cells
- Made from amino acids which join by peptide bonds into chains called polypeptides
47
Proteins: digestion
STOMACH (proteins → “pepsin” → small polypeptides)
SMALL INTESTINE (smaller peptides → “proteases” → peptides → “peptidases” → amino acids)
48
Nucleic Acid: types
- Ribonucleic Acid
| - Deoxyribonucleic Acid
49
Nucleic Acid: digestion
SMALL INTESTINE (DNA & RNA → “nucleases” → nucleotides → “nucleosidases” → sugars, phoshates)
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