Unit 12: Animal Structure and Function, Part A

1. Unit 12: Animal Structure and Function, Part A Chapters 40-44

2. Part A-Structure and Function • Thermoregulation • Digestive System • Respiratory SystemCirculatory SystemImmune System Excretory System Nervous SystemMuscular SystemEndocrine System

3. Part B-Repro. and Development • Sexual Characteristics • Human Reproductive Anatomy • Gametogenesis • Hormonal Control of Reproduction • Embryonic Development • Factors That Influence Development

4. Introduction • Recall that animals are multicellular, heterotrophic eukaryotes that obtain their energy/nutrition by ingesting other organisms. Our focus shifts to understanding why and how animals are so successful in so many habitats. • Animals are really just a complex system of cells working in a coordinated manner to monitor changing external conditions while maintaining a constant internal environment.

5. Introduction (cont’d) • To accomplish these tasks animal cells are organized into systems that are specialized for particular functions. These functions are properties that emerge from the specific shape and order of the given body parts. • Two major themes are exhibited by animals in this unit: • capacity to adjust over the long term to the environment by adaptation due to natural selection • capacity to adjust to the environment over the short term by physiological responses

6. 4 objectives for this introduction: • identify the hierarchy of structural order in animals • describe the importance of energetics • explain how body forms affect interactions with the external environment • analyze how regulation maintains favorable internal conditions

7. Levels of Structural Organization • Cell ---> Tissue ---> Organ ---> Systems • Tissues: groups of cells w/ common fxn. • Organs: organized tissues that function together • Organ systems: several organs with separate functions that act in a coordinated manner

8. Types of tissues • epithelial tissue (outer skin layers and internal protective coverings) • connective tissue (bone, cartilage, blood, adipose, loose and fibrous) • ** nervous tissue (specialized to conduct an impulse / bioelectric signal) • ** muscle tissue (consists of long, excitable cells that are contractile) • ** unique to animal kingdom/excitable tissue

9. Types of epithelial tissues • top exposed while bottom attached to basement membrane (basal lamina) • classified by number of cell layers . . . • simple vs. stratified (pseudostratified) • and the shape of free surface cells • cuboidal • columnar • squamous

10. Connective tissue fibers • collagenous • elastic • reticular

11. Major connective tissue types • loose • fibroblasts • macrophages • adipose • Fibrous (tendons and ligaments) • Cartilage • Bone • Blood - consists of liquid (plasma) and cells

13. Nervous Tissue • senses stimuli and transmits signals • neuron - a nerve cell (conducts impulses) • cell body • dendrites: conduct impulses to the cell body • axons: transmit impulses away from cell body

14. Parts of a Neuron

15. Types of muscle tissues • (a) skeletal • (b) cardiac • (c) smooth

16. Types of muscle tissues

17. Bioenergetics ! • BMR • basal metabolic rate • endotherms • SMR • standard metabolic rate • ectotherms

18. Body Plans

19. Regulation: Internal Environment • The function of most systems is to contribute toward homeostasis (maintenance of stable, internal conditions within narrow limits). Stable conditions are most often maintained by negative feedback.

20. Example of Homeostatic Control via Negative Feedback

21. How does it work? • A sensing mechanism (receptor) detects a change in conditions beyond specific limits. • A control center (integrator), often the brain, evaluates the change and activates a second mechanism (effector) to correct the condition. • In negative feedback, the original condition is canceled, or negated, so that conditions are returned to normal.

22. What about positive feedback? • There is also positive feedback, in which an action intensifies/amplifies a condition so that it continues beyond normal limits. • Examples – three physiological examples in humans…

23. Thermoregulation (2 groups) • Ectotherms (poikilotherms) • Endotherms (homeotherms)

24. Mechanisms for temp. regulation • evaporative cooling • warming via metabolism • adjusting surface area to regulate temperature • external surfaces • internal surfaces • countercurrent exchange

25. Chapter 41: Animal Nutrition • Nutritional Requirements • Food Types and Feeding Mechanisms • Overview of Food Processing • Mammalian Digestive System • Adaptations of Vertebrate Digestive Systems

26. Nutritional Requirements • animals are heterotrophs - they rely on organic compounds in their food • an adequate diet provides an animal with: • fuel (chemical energy) for cellular respiration • raw organic materials for biosynthesis • essential nutrients in prefabricated form

27. Mechanisms of fuel management • monomers from any of the complex molecules can be used as an energy source, carbos and fats are used first • oxidized fat produces 9.5 kcal/g= twice as rich in energy than either carbohydrates or proteins • excess calories are stored in the liver and muscles as glycogen; further excess is stored in adipose tissue as fat • deficiencies in caloric intake are met by using glycogen stores first, then fat stores, followed by the breakdown of the body’s own proteins.

28. Diet must supply essential nutrients and carbon skeletons • biosynthesis involves the processes used to make organic molecules • heterotrophs cannot use inorganic molecules to make organic ones; they require organic precursors. Examples: • single types of amino acids supply the necessary nitrogen to build other amino acids • fats are synthesized from carbohydrates • liver is the most important organ for the conversion of nutrients from one type of organic molecule to another

29. Diet (cont’d) • essential nutrients = chemicals an animal requires but cannot synthesize • an animal is malnourished if its diet is missing one or more essential nutrients: • essential amino acids: adult humans 12 + 8, infants 11+ 9; kwashiorkor - protein deficiency • essential fatty acids: humans - linoleic acid • vitamins: organic coenzymes (see Table 41.1) • minerals: inorganic nutrients (see Table 41.2)

30. Vitamins and Minerals • Vitamins are either water- or fat-soluble • water-soluble are not stored in the body; excesses are excreted in the urine • fat-soluble can be held in the body; excesses are stored in body fat; may accumulate to toxic levels and create a condition called vitaminosis • if an animal synthesizes a certain compound, it is not a vitamin (ascorbic acid: humans/rabbits) • Minerals may be structural (Ca), part of enzyme (Cu) or other molecules (Fe)

31. Food Types and Feeding Mechanisms • Animals usually ingest other organisms; parasites like tapeworms are an exception • herbivores eat autotrophic organisms • carnivores eat other animals • omnivores eat other animals and autotrophs • Feeding adaptations • suspension-feeders • substrate-feeders • deposit-feeders • fluid-feeders • bulk-feeders

32. Overview of Food Processing • 4 main stages of food processing • ingestion: the act of eating • digestion: process of breaking down food into particles that are small enough to absorb; hydrolytic enzymes cleave macromolecules into their monomers in special compartments • absorption: uptake of small molecules from digested material • elimination: undigested material passes out of the digestive compartment

33. Specialized Compartments • intracellular - food vacuoles are simple • organelles which digest food without having to mix hydrolytic enzymes with cell cytoplasm • extracellular - compartments are continuous with the outside of the body • gastrovascular cavity - one opening; functions both in digestion and nutrient distribution • complete digestive tracts, or alimentary canals, run between two openings; unidirectional flow means that regions of tube can be specialized

34. Mammalian Digestive System • consists of an alimentary canal and accessory glands that secrete digestive juices into the canal via ducts • peristalsis - smooth muscles move food • sphincters - ringlike muscle valves occur at important junctions and regulate movement • accessory glands - 3 pairs of salivary glands, pancreas, liver, and the gallbladder

35. Oral cavity and Pharynx • oral cavity - physical and chemical digestion begin here • chewing breaks food into smaller pieces to make it easier to swallow and to increase the surface area available to enzymes • salivary glands are stimulated by the presence of food to secrete saliva; contains mucin, buffers, antibacterial agents, and salivary amylase • pharynx - intersection for both the digestive and respiratory systems; movement of epiglottis blocks the glottis (windpipe) during swallowing

36. Esophagus • muscular tube connects stomach to pharynx • movement of bolus due to peristalsis • initial entrance is voluntary (swallowing); once in movement is due to involuntary contraction of smooth muscle • amylase remains active as the bolus moves through the esophagus

37. Stomach - (3 fxns.) • Food Storage - up to 2L • Churning - mixing of food with secretions • mixture is called acid chyme; passage into small intestine is controlled by pyloric sphincter • Secretion - controlled by parasympathetic nerve impulses and hormone - gastrin

38. 3 types of secretory gastric cells • mucous cells • release mucin and gastrin into bloodstream which stimulates further gastric secretions • chief cells • releases pepsinogen - the precursor to pepsin, a major proteolytic enzyme • releases zymogens - inactive proteases • parietal cells • secrete HCl - lowers stomach pH to 1-4

39. Small intestine - (2 fxns.) • digestion - hydrolytic enzymes and other secretions from 4 organs play a role • pancreas, liver, gallbladder, and the small intestine itself • most enzymatic activity occurs in the duodenum - the first 25 cm of the small int. • absorption of nutrients - through villi • villi and microvilli increase the absorptive surface area of the digestive tract (~300 m2) • occurs in the jejunum and ileum

40. Pancreas - a compound gland • endocrine, ductless gland - secretes insulin and glucagon hormones into the blood; not a digestive role • exocrine, ducted gland - secretes hydrolytic enzymes into the duodenum - break down all major classes of macromolecules; also secretes bicarbonate buffer to neutralize acid chyme

41. Liver - organ of many functions • for digestion, the liver produces bile, which: • is stored in the gallbladder • contains no digestive enzymes • contains bile salts which emulsify fats • contains pigments - the byproduct of broken RBCs in the bloodstream • emulsification - chemical reaction that converts fat globules into tiny fatty droplets and increases the enzymatic surface area

42. Major digestive enzymes in SI • carbohydrates - disaccharidases • proteins - zymogens are activated by enteropeptidase; converts trypsinogen to trypsin; trypsin activates more enzymes • nucleic acids - nucleases, nucleotidases • fats - emulsification; then acted on by pancreatic lipase

43. Absorption of monomers • nutrients are either diffused or actively transported across the epithelium and into capillaries • amino acids, sugars, and nucleotides diffuse easily into the bloodstream • glycerol and fatty acids are recombined in the epithelial cells to form fats • capillaries and veins drain nutrients from villi directly into the hepatic portal vein

44. Regulation of Digestion: Four Regulatory Hormones • gastrin: released from stomach as a response to the presence of food; stimulates the stomach to release gastric juices (pepsin and HCl) • secretin: released from duodenum; response to acid chyme entering from the stomach; signals the pancreas to release bicarbonate buffer • cholecystokinin (CCK): signals the gall bladder to release bile; pancreas to release enzymes • enterogastrone: response to the presence of fat in the chyme; inhibits peristalsis - slows digestion

45. Large intestine or Colon • connects to small intestine in a T junction • blind end of T is the cecum and ends with the fingerlike extension called the appendix • colon is shaped like an inverted U • ascending colon, transverse colon, descending colon • water reclamation is the large intestines major role • produces feces which are stored in the rectum and passed from the body

46. Adaptations of Vertebrate Digestive Systems • Structural adaptations of digestive systems are often associated with diet • dentition in mammals and nonmammals • length of the digestive system vs. diet • Symbiotic microorganisms aid nourishment • symbiotic bacteria and protozoa may make cellulase • housed in cecum (horse) cecum and colon (rabbit) or elaborate structure of ruminants

48. 42: Circulation in Animals • Primary Function: to pump oxygen and nutrient rich liquids throughout the internal environment • Types of circulatory systemsopen circulatory systemclosed circulatory system • Major Organs • Heart • Arteries/Veins/capillaries

49. Overview of Circulation • exchange of materials (nutrients, gases, or wastes) b/t animals and the environment take place across moist cell membranes • Problem of being 3-dimensional • some cells are isolated from the environment • solution: exchange organs coupled with a system for internal transport • transport systems connect the exchange organs w/ body cells

50. Why we need circulation • time of diffusion is proportional to the square of the distance travelled • ex. Glucose takes 1 second to diffuse 100 micrometers, therefore it will take 100 seconds to travel 1 mm. • The presence of a circulatory system reduces the distance a substance must diffuse to enter or leave a cell. • Most crucial for maintaining homeostasis