Chapter 41 Flashcards
What is nutrition?
food being taken in, taken apart, or taken up
All animals are heterotrophs, but…
they need to eat enough food and have a balanced diet to survive and reproduce
Three nutritional needs
- Fuel for cells
- Organic materials for biosynthesis
- Essential nutrients
Fuel for cells
ATP
Organic materials for biosynthesis
proteins, carbohydrates, lipids, and nucleic acids
carbohydrates
sugars
lipids
fats
Essential nutrients
cannot by synthesized, must be consumed
Examples of essential nutrients
some amino acids, fatty acids, and vitamins and minerals
Malnutrition
occurs when diet lacks one or more essential nutrient or consistently supplies less energy than body needs
What can malnutrition cause?
deformities, disease, death
Undernutrition
occurs when diet lacks adequate sources of chemical energy (carbs, protein, lipids)
When are humans considered undernourished?
If they consume less than the recommended 2,200 kcals/day
Kwashiorkor
occurs mainly in children whose diet lacks high quality protein
Marasmus
caused by a diet low in protein and calories
Characterized by discolored skin and bloated stomach
Kwashiorkor
Characterized by being very thin, shriveled with low resistance to infection
Marasmus
Ingestion
the act of eating/feeding
Hydrolysis
using water to break down food
Digestion
breakingn down food into absorbable molecules
Two types of digestion
- Mechanical digestion
2. Chemical digestion
Mechanical digestion
breaks food into smaller pieces (chewing)
Chemical digestion
chemical breakdown of food particles into nutrients via enzymes
What are nutrients used for?
energy and biosynthesis
Protiens
amino acids
Carbohydrates
sugars
Lipids
fatty acids and glycerol
Absorption
cells take up (absorb) nutrients through the bloodstream
Steps to processing food
- Ingestion
- Digestion
- Absorption
- Elimination
Elimination
undigested material exits through the digestive track
How is it that animals do not digest their own cell tissues?
Digestive compartments
Digestive compartments
food processing happens in specialized areas of the body to prevent enzymes from breaking down animals’ own tissues
Digestion can be…
Intracellular or extracellular
Intracellular digestion
food particle engulfed by the cell
Where does intracellular digestion occur?
within organelles that contain digestive enzymes
Extracellular digestion
occurs outside cells in a specialized compartment and is continuous with exterior
When is food “inside” the body
nutrients cross a layer of cells (absorption)
Two types of extracellular digestion
- Gastrovascular cavity
2. Alimentary canal
Step 1 of the Gastrovascular cavity
Digestive enzymes are released from a gland cell
Step 2 of the gastrovascular cavity
enzymes break food down into small particles
Step 3 of the gastrovascular cavity
food particles are engulfed and digested in food vacuoles
Gastrovascular cavity
digestive sac with a single opening that functions as a mouth and anus
What does the gastrovascular cavity function in?
digestion and circulation of nutrients
Where is gastrovascular cavity observed in?
simple animals
Alimentary canal
- complete digestive tract
- two openings
- food moves in one direction
- specialized regions for different tasks
Two openings in alimentary canal
mouth and anus
Accessory glands of alimentary canal
secrete digestive juices through ducts into the canal
4 types of accessory glands
- Salivary glands
- Liver
- Pancreas
- Gullbladder
Peristaisis
alternate waves of contractions and relaxation in the smooth muscle lining the canal
What does the peristaisis do?
propels food
Sphincters
muscular valves that regulate passage of material between segmenets
What occurs in the oral cavity
mechanical digestion and chemical digestion
Mechanical digestion increases…
SA
What occurs during chemical digestion?
- Salivary glands release saliva
2. Salivary amylase begins carb digestion
What does the tongue do?
shapes the food into a bolus and pushes it to the pharynx
Pharynx
“throat,” opens to trachea and esophagus
Epiglottis
blocks trachea during swallowing
Esophagus
moves food from pharynx to stomach
What types of muscles near top of esophagus?
Skeletal (swallowing)
What type of muscles in the middle to lower esophagus?
Switches to smooth (involuntary contractions (peristalsis))
Stomach
food storage
the stomach is where the preliminary digestion of ____ occurs
proteins
What is the stomach lined with
epithelial tissue
Where do stomach pits lead to?
gastric glands that secrete gastric juice
Gastric juice mixes with food to form ____
chyme
Chief cells
secrete pepsinogen
Where are chief cells found?
stomach
Pepsinogen
protein digesting enzyme (protease)
What does pepsinogen break?
long protein chains into smaller chains
Parietal cells
secrete HCI and gives gastric juice low pH (2)
Where are parietal cells
stomach
What do parietal cells disrupt?
the extracellular matrix that binds cells together in meat and plant mater
What does parietal cells kill
bacteria
What do parietal cells unfold
protein
What does parietal cells convert pesinogen into
active pepsin
Mucus cells
secrete mucus
What do mucus cells do for the stomach?
lubricates and protects stomach lining from gastric juice
What do chief cells release?
pepsinogen
What do parietal cells do?
release HCI and convert pepsinogen into pepsin
Where are pepsin and HCI formed?
outside of cells (in lumen)
What does mucus secreted by mucous cells do?
protects stomach ining from gastric juice
Contents of the stomach are mixed by…
smooth muscles
The stomach combines…
food and enzymes into acid chyme
Chyme then moves to…
the small intestine
what is the small intestine controlled by?
Pyloric sphincter
Small intestine
longest compartment of alimentary canal
The small intestine is the site of..
most digestion and ALL nutrient absorption
The small intestine consists of the…
- duodenum
- jejunum
- lleum
Duodenum (first 25 cm)
digestion completes in this section
What occurs in the duodenum?
Chyme mixes with digestive juices from pancreas, liver, gallbladder, and small intestine
Two portions of the pancreas
- endocrine
2. exocrine
Endocrine
directly to bloodstream
- insulin and glucagon
Exocrine
ducts
- digestive secretions
Digestive secretions
bicarbonate-rich alkaline (basic) solution that buffers acidic chyme
Hydrolytic enzymes
- Pancreatic amylases
- Pancreatic trypsin and chymotryspin
- Pancreatic nucleases
- Pancreatic lipases
Pancreatic amylases
carbohydrates
pancreatic tryspin and chymotryspin
proteins
pancreatic nucleases
nucleic acids
pancreatic lipases
lipids
Liver
produces bile that is stored in the gallbladder
Bile
contains bile salts that serve to break down lipids (emulsifiers)
Where does absorption take place
jejunum and ileum of small intestine
What forms villi
folds in the epithelial tissue lining the intestine
microvilli
tiny projections each cell has
What do villi and microvilli do together
increase surface area for nutrient absorption
What does the core of each vilus contain?
blood vessels andn a lacteal for nutrient distribution
Sugars and amino acids
enter blood stream directly
What do capillaries and veins converge to form?
Hepatic portal vein
Where do hepatic portal veins carry nutrient rich blood?
directly to the liver where detoxification occurs
Where do nutrients from from the liver to?
the heart, where they are then pumped to toher tissues in the body
what are fats repackaged into and where do they enter?
they are repackaged into chylomicrons and enter lacteals (lmphatic vessels)
Where does the lymphatic system eventually carry chylomicrons to?
large veins that return blood to the heart
What does teh large intestine consist of?
- cecum
- colon
- rectum
cecum
ferments ingested material
appendix
a projection of cecum and plays a minor role in immunity
colon
leads to rectum and anus
what is the colon responsible for?
reabsorption of water to produce feces - fiber hels move food along
rectum
stores feces until elimination
Three adaptations the text covers
- dental adaptations
- stomach and intestinal adaptations
- mutualistic adaptations
Carnivore
kill, rip, tear, shred
Herbivore
bite veg. and grind
Omnivore
bladelike incisor-bite, pointed canines-tear molars-grind/crush
Digestive system of carnivores
relativel short digestive tract for absorbing nutrients from meat
Digestive system of herbivore
relatively long (more time and surface area for absorption)
Why do carnivores also have large expandable stomachs?
uncertainty of meals so they eat as much as they can
Why do herbivores also have long cecum with bacteria
to facilitate digestion of plant material
Enteric division of the nervous system
activates parts of the digestive system at the appropriate time
What does the enteric division of the nervous system trigger?
secretion of substances that promote next stage of digestion
What does enteric division stimulate?
peristalsis
Endocrine system
secretes hormones that control digestive secretions
What does energy from food replace?
energ lost during metabolism, activity, and storage
Excess nutrients are stored…
sugars are stored as glycogen in liver and muscle
Once glycogen stores are full…
excess sugar is converted to fat and stored in adipose tissue
Glucose
the primar fuel for cells
What does regulation of glucose rely on?
opposing effects of insulin and glucagon
Where is glucose produced in?
pancreatic islets
alpha cells
produce glucagon
beta cells
produce insulin
Concequence of disrupted glucose homeostasis
- deficiency of insulin (type 1)
2. decreased response to insulin (type 2)
Blood glucose levels rise but…
cells cannot take up enough to meet metabolic needs
What becomes the main energy source when blood glucose levels rise?
fat
Excess glucose in the blood excreted in…
the urine
Whater excreted with the glucose, leading to:
- increased urination
- increased thirst
- increased hunger
Type 1
- usually begins in childhood
- body destroys beta cells, leading to lack of insulin
- treated with insulin injections
Type 2
- usually begins later in life
- target cells do not respond to insulin, and therefore do not uptake glucose
- often can be treated with diet and exercise, some patiente require medication
Feedback loops and hormones control appetite, nutrient storage, and me tabolism
- Grehlin
- PYY
- Insulin
- Leptin
Grehlin
secreted by stomach wall when empty
triggers feelings of hunger
PYY
secreted by small intestine after meals
suppresses appetite
Insulin
Secreted by pancrease after meals
Suppresses appetite
Leptin
Produced by adipose tissue
Suppresses appetite
