Digestive System
and
Excretory System
Process of Digestion
Function:
- help convert or break down foods into
simpler molecules that can be absorbed
and utilized by the cells
Two types of digestion:
1. mechanical – physical breakdown by
tearing or grinding
2. chemical – breakdown of food with
enzymes or substances that dissolve
Organs of Digestion
• Pathway of
digestion:
• Mouth (pharynx)
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Rectum
• Anus
Organs of Digestion
• Mouth – food enters and undergoes both mechanical
and chemical digestion
- Teeth will tear and mash food particles for
break down
- Salivary glands produce saliva that contains
enzymes that will dissolve food (sugars and
amylase)
• Esophagus – long tube that connects mouth to the
stomach
- no digestion takes place in the esophagus
- peristalsis is the rhythmic contractions that take
place to move food down to the stomach
Organs of Digestion
• Stomach – large muscular sac
where both mechanical and
chemical digestion take place
- contractions of wall churn and
mix food
- Hydrochloric Acid (HCl)
chemically breaks down bolus
and activates an enzyme called
pepsin that will break down
proteins
- makes the environment acidic
- kills some microorganisms
Organs of Digestion
• Small Intestine – long narrow tubing where
chemical digestion and absorption take place
- coiled and compacted to fit, but measures 4
times the height of the individual
- consists of the duodenum, jejunum, and
ileum
- materials that pass undigested in small
intestine go to appendix, that mainly stores
cellulose
Organs of Digestion
• Large intestine – larger diameter tubing that
measures equal to the height of an individual
- primary function is to remove water from
undigested material
- solid waste will then leave colon and pass
through the rectum and exit the body
Accessory Organs
• Liver, Gallbladder, and Pancreas are organs that
aid in chemical digestion
- liver produces bile which breaks down fats
- gallbladder stores and releases bile
- pancreas produces alkaline buffers to
combat acidic environment
- all are accessory because no actual food
passes through these organs
- fluids produced by these organs are released
into the duodenum of the small intestine
Excretory System
• Excretion is the process in which the body
eliminates metabolic wastes
• Excretion is a homeostatic process of the body
• Skin and lungs are other organs that are
considered part of excretory system for
removing wastes
Kidneys
Kidneys are the main organ of
excretion
- remove waste products
- maintain blood pH
- regulate water content of the
blood
- act as a filter for separating
toxic substances (nitrogen) and
converting it to urea
- also send needed products
back into bloodstream
Elimination of Wastes
• Pathway of waste:
1. Waste products are
filtered and separated in
the kidney
2. Waste moves to the
ureters which connect to
the bladder
3. Bladder is an inflatable
sac that fills with a little less
than 2 liters of fluid (urine)
4. Waste leaves bladder
and enters urethra to be
removed from the body