Human Digestive System. Ingest food Break down food Move through digestive tract Absorb digested...
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Transcript of Human Digestive System. Ingest food Break down food Move through digestive tract Absorb digested...
Human Digestive System
Ingest food Break down food Move through digestive tract Absorb digested food and water Eliminates waste materials HowStuffWorks Videos "Assignment
Discovery: Breaking Down Digestion"
1. Ingestion
Eating and drinking
2. Digestion 2 kinds
1. Mechanical Digestion chewing, chopping, grinding breaks food into smaller pieces increases surface area for:
2. Chemical Digestion breaks chemical bonds within macronutrients hydrolysis reaction (releases water) BiologySource
Mouth Breaks down food
into small pieces Begins starch
digestion (amylase) Saliva produces
amylase and lubricates food
Moves food into esophagus
Epiglottis covers trachea
Peristalsis moves food to stomach
Oesophagus (esophagus) ~ 24 cm long tube takes food from
pharynx to stomach made up of circular,
longitudinal & smooth layers of muscles
work together to push food along
Peristalsis circular & longitudinal
muscles contract rhythmically
lubricant mucin added
together push bolus (ball of food) along in waves to stomach
Peristaltic Wave in the Gastric Antrum - YouTube
Stomach First opening – cardiac sphincter Muscles churn food – more mechanical digestion Inner layer folded into ridges called rugae that
contain gastric glands Glands produce gastric juice = pepsin + HCl Mucous secreted that protects stomach wall Pepsin breaks down proteins (only at pH 2) creates chyme (thick liquid), which leaves after
2-4 hrs Second opening – pyloric sphincter Stomach Digestion - YouTube
3. Absorption proteins, starches, sugars, fats
& vit.Small Intestine: ~ 7 m long chyme leaves stomach into
duodenum jejunum middle section illium passes chyme into lg
intestine lined with finger-like villi (inc
SA) each villus had artery, vein &
lymph vessels to it nutrients absorbed into blood
by diffusion or active transport
Large Intestine (aka the colon)
~ 1.5 m long absorbs water from wastes e. coli bacteria further break down
wastes (produce methane) other bact. produce vitamin B & K
which get absorbed
4. EliminationLarge Intestine, Rectum &
Anus Rectum - last 20-30 cm of LI stores wastes (toxins) when fills with wastes nerves
send message to brain to empty wastes exit through anal
sphincter low cellulose (fibre) diet results
in less elimination, so toxins in rectum for longer
increased risk of colon cancer
Endocrine Glands
Pancreas, Liver & Gall Bladder
* chyme doesn’t enter these organs but they help in digestion*
Pancreas produces: insulin lowers blood glucose glucagon raises bld glucose pancreatic juices & NaHCO3:
Digestive Enzymes (Pancreas)
neutralize chyme & contain digestive enzymes
break down macromolecules
Ex: Protease – protein into a.a. Lipase – fat into glycerol
and 3 fatty acids Maltase, Sucrase, Lactase –
sugars into glucose
Liver & Gall BladderLiver: produces bile which
contains salts to break down lg fat globules (inc. SA)
stores carbs and vitamins detoxifies Gall Bladder: stores bile until needed Digestive System.notebook