Nutrition and Digestion Chapter 21 Nutrition and Digestion

Humpback whale Can eat up to 2 tons of krill and fish in a day which allows them to harvest much more energy than they need In cold weather they migrate to breed in warmer waters They do not need to eat or hardly eat during these 4 months

Ways of ingesting food for animals

Ways of ingesting food for animals continued Suspension feeders: extract food from particles in fluid/ examples: humpback whale, clams, oysters Substrate feeders: live in or on their food source and eat their way through it/ example: earthworm Fluid feeders: obtain food by sucking nutient-rich fluids from a living host/ ex. mosquitoes Bulk feeders: ingest their food in large pieces/ example: grey heron

Food processing ingestion: the act of eating Digestion: breaking down food into smaller pieces (physical and chemical) Absorption: the take up of the products of digestion Elimination: undigested materials exit the digestive tract

Specialized compartments of digestion Gastrovascular cavity: just a mouth Alimentary canal: mouth and an anus Pharynx: throat Esophagus: tube that channels food Crop: softens and stores food Stomach: churn and grind food Gizzard: churn and grind food Intestine: chemical digestion and nutrient absorption Anus: expels undigested food

Human digestion: the oral cavity Saliva is released before a bite is even taken Salivary glands release more than a liter of saliva a day A glycoprotein protects the soft lining of the mouth and lubricates food for easier swallowing Saliva contains salivary amylase which begins to breakdown the carbs the food Buffers neutralize the food to prevent tooth decay Mechanical and chemical digestion occur here Tongue: muscular organ that is covered in taste buds and pushes the bolus of food to the back of the oral cavity and into the pharynx

Oral cavity Blade like incisors (2): Used for biting Single pointed canine: used to rip apart food Premolars (2): grind and crush food Molars (3): grind and crush food

Food path continued Oral cavitybolus to the back of the oral cavity bolus down the pharynx down the esophagus by way of peristalsis

Stomach Secretes gastric juices made up of mucous, enzymes and strong acids/ pH of 2/ breaks apart the particles of food Pepsin begins the chem. Digestion of proteins/ breaks down large polypeptides into smaller polypeptides The stomach takes about 2-6 hours to empty after a meal

Small Intestine The rest of chemical digestion occurs here More than 6 m in length Sources of digestive enzymes in the sm intestine: pancreas, liver, gallbladder First 25 cm of sm intestine is the duodemnum

Digestion in the small intestine Starch (pancreatic amylase)maltose (maltase)monosaccharides Polypeptides (trypsin, chymotrypsin) smaller polypeptides (aminopeptidase, carboxypeptidase, dipeptidase) amino acids DNA and RNA (nucleases)nucleotides (other enzymes)N-bases, sugars and phosphates Fat (bile salts)fat droplets (lipase)fatty acids and glycerol

Absorption in the small intestine Use microvilli which are finger-like projections that increase surface area for absorption Some materials are absorbed through simple diffusion

Liver Hepatic portal vein: the large vessel that transport nutrients absorbed from the small intestine right into the liver Regulates the amount of glucose released into the blood Plays a large role in the body’s metabolism Aids in the digestion of fats Detoxifies and modifies substances

Large Intestine AKA colon Reabsorbs water from undigested foods As water is absorbed the remaining undigested materials remains a solid (feces) Feces is eliminated through the rectum