AN INTRODUCTION TO ANIMAL STRUCTURE AND FUNCTION

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AN INTRODUCTION TO ANIMAL STRUCTURE AND FUNCTION
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Introduction

• Anatomy is the study of the structure of an
  organism.
• Physiology is the study of the functions an
  organism performs.
• Animals are multicellular organisms with their
  specialized cells grouped into tissues.
• In most animals, combinations of various tissues
  make up functional units called organs, and
  groups of organs that work together form organ
  systems.
• For example, the human digestive system consists
  of a stomach, small intestine, large intestine,
  and several other organs, each a composite of
  different tissues

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Organization

• Tissues are groups of cell with a common
  structure and function.
• Different types of tissues have different
  structures that are especially suited to their
  functions.
• A tissue may be held together by a sticky
  extracellular matrix that coats the cells or
  weaves them together in a fabric of fibers.
• Tissues are classified into four main categories
  epithelial tissue, connective tissue, nervous
  tissue, and muscle tissue.

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Epithelial Tissue

• Sheets of tightly packed cells, epithelial tissue
  covers the outside of the body and lines organs
  and cavities within the body
• riveted together by tight junctions.
• functions as a barrier protecting against
  mechanical injury, invasive microorganisms, and
  fluid loss.
• free surface of the epithelium is exposed to air
  or fluid, and the cells at the base of the
  barrier are attached to a basement membrane, a
  dense mat of extracellular matrix.
• classified by the number of cell layers and the
  shape of the cells on the free surface

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Types
simple epithelium has a single layer of cells,
and a stratified epithelium has multiple
layers The shapes may be cuboidal (like dice),
columnar (like bricks on end), or squamous (flat
like floor tiles).
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Epithelial Examples

• glandular epithelia lining tubules in the thyroid
  gland secrete a hormone that regulates fuel
  consumption.
• glandular epithelia that line the lumen of the
  digestive and respiratory tracts form a mucous
  membrane that secretes a slimy solution called
  mucus that lubricates the surface and keeps it
  moist.
• epithelial surfaces of some mucous membranes have
  beating cilia that move the film of mucus along
  the surface.
• Ex. Lungs have cilia to sweep away debris and
  invaders

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Connective Tissue

• Connective tissue functions mainly to bind and
  support other tissues.
• Connective tissues have a sparse population of
  cells scattered through an extracellular matrix.
• Matrix consists of a network of fibers embedding
  in a uniform foundation that may be liquid,
  jellylike, or solid.
• most abundant tissue type
• 3 kinds of connective tissue fibers, which are
  all proteins collagenous fibers, elastic fibers,
  and reticular fibers.

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Connective Cont

• Collagenous fibers are made of collagen.
• Collagenous fibers are nonelastic and do not tear
  easily when pulled lengthwise.
• Elastic fibers are long threads of elastin.
• Elastin fiber provide a rubbery quality.
• Reticular fibers are very thin and branched
• major types of connective tissues in vertebrates
  are loose connective tissue, adipose tissue,
  fibrous connective tissue, cartilage, bone, and
  blood.

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Nervous Tissue

• senses stimuli and transmits signals from one
  part of the animal to another.
• The functional unit of nervous tissue is the
  neuron, or nerve cell.
• made of a cell body and two or more extensions,
  called dendrites and axons.
• Dendrites transmit nerve impulses from their tips
  toward the rest of the neuron.
• Axons transmit impulses toward another neuron or
  toward an effector, such as a muscle cell.

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Muscle Tissue

• composed of long cells called muscle fibers that
  are capable of contracting when stimulated by
  nerve impulses.
• muscle fibers are large numbers of myofibrils
  made of the contractile proteins actin and
  myosin.
• muscle contraction accounts for most of the
  energy-consuming cellular work in active animals
• 3 types of muscle tissue in the vertebrate body
  skeletal muscle, cardiac muscle, and smooth
  muscle.

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Next Level of Organization

• In all but the simplest animals (sponges and some
  cnidarians) different tissues are organized into
  organs.
• vertebrate organs are suspended by sheets of
  connective tissues called mesenteries in body
  cavities moistened or filled with fluid.
• some organs the tissues are arranged in layers.
• For example, the vertebrate stomach has four
  major tissues layers.

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Organ Systems and Functions
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Overview How it all Works
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Digestive System

• Feeding Types Herbivores, such as gorillas,
  cows, hares, and many snails, eat mainly
  autotrophs (plants, algae).
• Carnivores, such as sharks, hawks, spiders, and
  snakes, eat other animals.
• Omnivores, such as cockroaches, bears, raccoons,
  and humans, consume animal and plant or algal
  matter.
• most animals are opportunistic, eating foods that
  are outside their main dietary category when
  these foods are available.
• For example, cattle and deer, which are
  herbivores, may occasionally eat small animals or
  birds eggs.

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Ways of Eating

• suspension-feeders that sift small food particles
  from the water.
• Deposit-feeders, like earthworms, eat their way
  through dirt or sediments and extract partially
  decayed organic material consumed along with the
  soil or sediments.
• Substrate-feeders live in or on their food
  source, eating their way through the food.
• Ex, maggots burrow into animal carcasses and leaf
  miners tunnel through the interior of leaves.

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Cont..

• Fluid-feeders make their living sucking
  nutrient-rich fluids from a living host and are
  considered parasites.
• Mosquitoes and leaches suck blood from animals.
• Aphids tap the phloem sap of plants.
• Most animals are bulk-feeders that eat relatively
  large pieces of food.
• Their adaptations include such diverse utensils
  as tentacles, pincers, claws, poisonous fangs,
  and jaws and teeth that kill their prey or tear
  off pieces of meat or vegetation.

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Digesting What Ya Ate

• The main purpose of the digestive system is to
  breakdown food for fuel, carbon skeletons, and
  essential nutrients
• four main stages of food processing are
  ingestion, digestion, absorption, and elimination
• To avoid digesting their own cells and tissues,
  most organisms conduct digestion in specialized
  compartments.
• Done many different ways in the animal
  kingdom!!!!!!! We will focus on mammals

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Digestive System

• mammalian digestive system consists of the
  alimentary canal and various accessory glands
  that secrete digestive juices into the canal
  through ducts
• Peristalsis, rhythmic waves of contraction by
  smooth muscles in the walls of the canal, push
  food along.
• Sphincters, muscular ringlike valves, regulate
  the passage of material between specialized
  chambers of the canal.
• The accessory glands include the salivary glands,
  the pancreas, the liver, and the gallbladder

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From Start to Finish

• physical and chemical digestion of food begins in
  the mouth.
• teeth of various shapes cut, smash, and grind
  food, making it easier to swallow
• Salivary glands secrete saliva that contains
  salivary amylase, an enzyme that starts the
  breakdown of sugar.
• tongue tastes food, manipulates it during
  chewing, and helps shape the food into a ball
  called a bolus.
• pharynx, also called the throat, is a junction
  that opens to both the esophagus and the trachea

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Cont

• When we swallow, the top of the windpipe moves up
  so that its opening, the glottis, is blocked by a
  cartilaginous flap, the epiglottis.
• This mechanism normally ensures that a bolus will
  be guided into the entrance of the esophagus and
  not directed down the windpipe.
• esophagus conducts food from the pharynx down to
  the stomach by peristalsis.
• stomach stores food and performs preliminary
  digestion
• stomach is located in the upper abdominal cavity,
  just below the diaphragm. Hold 2L of Food
• The stomach also secretes a digestive fluid
  called gastric juice and mixes this secretion
  with the food by the churning action of the
  smooth muscles in the stomach wall.

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Cont..

• high concentration of hydrochloric acid, the pH
  of the gastric juice is about 2 - acidic enough
  to digest iron nails.
• pepsin, an enzyme in the stomach begins the
  breakdown of proteins.
• coating of mucus, secreted by epithelial cells,
  that protects the stomach lining
• epithelium is continually eroded, and the
  epithelium is completely replaced by mitosis
  every three days.
• Side Note Gastric ulcers, lesions in the
  stomach lining, are caused by the acid-tolerant
  bacterium Heliobacter pylori.
• Ulcers are often treated with antibiotics
• it takes about 2 to 6 hours after a meal for the
  stomach to empty

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Cont..

• small intestine is the major organ of digestion
  and absorption
• length of over 6 m in humans, the small intestine
  is the longest section of the alimentary canal.
• In the first 25 cm or so of the small intestine,
  the duodenum, acid chyme from the stomach mixes
  with digestive juices from the pancreas, liver,
  gall bladder, and gland cells of the intestinal
  wall
• pancreatic amylase splits glycogen into
  disaccharides
• pancreatic lipase breaks down triglycerides
• trypsin, chymotrypsin, and carboxypeptidase
  digest proteins
• nucleases digest nucleic acids
• bicarbonate ions make pancreatic juice
  alkaline pH now 8

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Working Together
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Cont

• Most digestion occurs in the duodenum.
• The other two sections of the small intestine,
  the jejunum and ileum, function mainly in the
  absorption of nutrients and water.
• small intestine has a huge surface area - 300 m2,
  roughly the size of a tennis court. Increase
  surface area increase reaction rate
• transport of nutrients across the epithelial
  cells is passive, in some cases, as molecules
  move down their concentration gradients from the
  lumen of the intestine into the epithelial cells,
  and then into capillaries

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Cont

• Other nutrients, including amino acids, small
  peptides, vitamins, and glucose, are pumped
  against concentration gradients by epithelial
  membranes.
• This active transport allows the intestine to
  absorb a much higher proportion of the nutrients
  in the intestine than would be possible with
  passive diffusion
• We absorb 80 to 90 percent of the organic
  material in their food.
• The active mechanisms of digestion, including
  peristalsis, enzyme secretion, and active
  transport, may require that an animal expend an
  amount of energy equal to between 3 and 30 of
  the chemical energy contained in the meal.

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Cont

• Reclaiming water is a major function of the large
  intestine
• large intestine, or colon, is connected to the
  small intestine at a T-shaped junction where a
  sphincter controls the movement of materials.
• One arm of the T is a pouch called the cecum. the
  appendix, fingerlike projection of cecum, makes a
  minor contribution to body defense
• Over 90 of the water is reabsorbed, most in the
  the small intestine, the rest in the colon.
• Digestive wastes, the feces, become more solid as
  they are moved along the colon by peristalsis.
• Movement in the colon is sluggish, requiring 12
  to 24 hours for material to travel the length of
  the organ.
• Diarrhea results if insufficient water is
  absorbed and constipation if too much water is
  absorbed

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Bacterial Help

• Living in the large intestine is a rich flora of
  mostly harmless bacteria.
• One of the most common inhabitants of the human
  colon is Escherichia coli, a favorite research
  organism.
• As a byproduct of their metabolism, many colon
  bacteria generate gases, including methane and
  hydrogen sulfide.
• Some bacteria produce vitamins, including biotin,
  folic acid, vitamin K, and several B vitamins,
  which supplement our dietary intake of vitamins.

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End of the Road

• The terminal portion of the colon is called the
  rectum, where feces are stored until they can be
  eliminated.
• Between the rectum and the anus are two
  sphincters, one involuntary and one voluntary
• Finally evolution has provided many ways for
  animals to get and digest their food. Compare
  carnivore to herbivore, different ways of getting
  food like snakes jaws, and different symbiotic
  bacteria used by different organisms, and

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Differences but same Goal!!
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Overview
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References

• Jack Brown M.S. Biology
• Shier,David, Jackie Butler, Ricki Lewis Holes
  Human Anatomy and Physiology 10th edition 2004
  McGraw-Hill
• Marieb, Elaine Essentials of Human Anatomy and
  Physiology 7th edition. 2003 Pearson Education
  Inc Benjamin Cummings pub.
• Microsoft Encarta Encyclopedia 2004
• Starr and Taggart The Unity and Diversity of
  Life 10th edition 2004 Thomson Brookes/Cole
• Campbell and Reece Biology 6th edition 2002
  Benjamin Cummings.
• Raven and Johnson Holt Biology 2004 Holt,
  Rinehart and Winston.