BSC 1010 - General Biology I

Digestive System (Animal Nutrition)

Reading Assignment: POHS pp. 1038-1065

Self Quiz: 1, 3 - 8

Applying Concepts: None; Question 4 is down right scary as it suggests the pancreatic enzymes empty into the bile duct rather than the hepatopancreatic ampulla.

Additional thought questions:

1) Name and describe two mechanisms which prevent the gut tract from digesting itself.

Lecture outline:

All animals are heterotrophs
	derive energy and essential nutrients from other organisms
	nutritional requirements
		energy - molecules used to produce ATP (carbohydrates, lipids, amino acids)
			measured in Calories (= kilocalories)
			stored as glycogen (carbohydrate) - short term
			stored as fat - long term
		molecular building blocks - basic organic molecules (carbon skeletons) that 
				cannot be synthesized; e.g., acetyl groups
			specific ones required vary between organisms
			used to construct other necessary compounds (e.g., fatty acids, steroid 
				hormones, etc.)
			includes essential amino acids
			includes essential fatty acids
		specific biochemical functions
			mineral elements - Table 47.1
			vitamins - Table 47.2
				most function as coenzymes

Adaptations for feeding
	wide variety of nutritional lifestyles
		detritivores
		predators
			herbivores
			carnivores
			omnivores
	feeding mechanisms
		filter feeding
		fluid feeding
		substrate feeding
		bulk feeding

Digestion - the breakdown of food substances into simpler molecules
	3 types of digestive systems
		intracellular 
		pseudo gut - combination of intra-and extra-cellular
		true gut or tubular gut - digestion is extracellular

Mechanisms of extracellular digestion
	acid digestion
	enzymatic digestion
	mechanical reduction
	fermentation - use of symbiotic microorganisms

Overview of the vertebrate digestive system
	oral or buccal cavity
	alimentary canal
		generalized structure
			lumen
			mucosa
			submucosa
			muscular layer
			serosa (except in esophagus)
	accessory organs - liver, gall bladder, pancreas

Movement of food through the digestive system
	swallowing or deglutition
	peristalsis

Structure and function of the vertebrate digestive system
	oral cavity - mechanical and enzymatic digestion
	stomach - storage; mechanical, acid and enzymatic digestion
	small intestine - subdivisions
		duodenum - largely digestive
			enzymatic digestion (Table 47.3) - pancreas and small intestine
			bile - produced in liver, stored in gall bladder, secreted to duodenum; 					emulsifies fat
		ileum and jejunum - largely absorptive
	large intestine (colon) - site of water and ion absorption
		bacterial symbionts
		vermiform appendix 

Digestion of cellulose
	enzyme cellulase not present in vertebrate gut
	dependent upon symbiotic bacteria (fermentation)
	mammals:  foregut and hindgut fermentors
		ruminant stomach 

Control and regulation of digestion
	Gut controlled by both nervous and endocrine systems
	Nervous system 
		CNS - extrinsic
		enteric nervous system - intrinsic
	Endocrine system - hormones
		most are local (non-systemic), acting within digestive tract
		e.g., gastrin, cholecystokinin, secretin

Control and regulation of fuel metabolism - skip in the interest of time

Nutrient deficiency diseases 
	Funk the concept of dietary diseases (not a new rock group)
		beriberi
	kwashiorkor
	scurvy
	pellegra
	rickets
	pernacious anemia
	goiter

Toxic compounds in food
	hydrophilic vs lipophilic
	bioaccumulation 
	synthetic toxins

Topics not covered in lecture for which you will be responsible:

	undernourishment and overnourishment - p. 1041
	malnutrition - 1041
	zymogens - p. 1049 and Fig. 47.15
	digestion and absorption of fat - p. 1055 and Fig. 47.16
	VLDL, LDL and HDL - p. 1058