Lecture 9,12,13 for Vertebrate Anatomy
Lecture 9,12,13 for Vertebrate Anatomy Biol 161A
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This 21 page Class Notes was uploaded by Anastassia Erudaitius on Monday February 29, 2016. The Class Notes belongs to Biol 161A at University of California Riverside taught by Dr. Reznick in Fall 2015. Since its upload, it has received 33 views. For similar materials see FUNCTIONAL ANATOMY: VERTEBRATES in Biology at University of California Riverside.
Reviews for Lecture 9,12,13 for Vertebrate Anatomy
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Date Created: 02/29/16
Vertebrate Anatomy – Biol 161A Lecture 9 – Bone Composition and Muscles From previous sections Monophyletic groups – defined by shared derived characters that distinguish them from other vertebrate classes Vertebrates look the way they do because: 1 Who they are – their shared derived traits 2 They are adapted for specific lifestyles Lecture Notes Bone is dynamic, not static (capable of change during life of individual) o It is made up of many materials, and together give bone certain properties that its single components do not have alone o Stores salts – mainly calcium phosphate o Can be remodeled (necessary for growth, healing, and flexibility required to respond to external stress) Fine Structure of bone o Composite materials that make up bone: Hydroxyapatite (calcium phosphate crystals complexed with water molecules) Ca4O Proteins various forms of collagen Both materials are interwoven crystals are small and flat and separated by layers of protein Mineral content varies considerably 1 Red = mineral Blue = protein Properties of the composite materials: o Together the protein and mineral give the bone rigidity and flexibility o Small crystals of hydroxyapatite are suspended in a flexible protein matrix o Protein gives flexibility o Crystal hydroxyapatite gives rigidity o Properties can be varied with the degree of mineralization More minerals = stronger bone but less flexible Cell types o Osteoblasts – build bone Osteocytes – class of osteoblasts that are found within pockets of the bone rather than on the surface 2 o Osteoclasts – digest/ break down bone Secrete acids that dissolve the hydroxyapatite crystals and secrete enzymes that digest the protein Remodeling bone = building or breaking down bone o Osteoblasts and Osteoclasts allow bone to be remodeled allow bone to be in equilibrium with the rest of the body o Allows a way to store and then reutilize calcium salts Required for muscle contraction and transmission of nerve impulses Concentration of calcium ions is closely regulated Being able to build or break down bone allows the body to maintain equilibrium in ion concentration Bone growth o Growth of long bones requires adding and subtracting to different surfaces of the bone as bone grows the bone on the inside is subtracted and added to the outside o Adding and subtracting bone evident in marching, rooted teeth in manatee or elephant (teeth move forward as they get worn down, plate forms at front then falls out) roots of front teeth get absorbed and leave plate behind Healing bone fractures o New bone is built where breaks occur and fuses broken ends together Adaptation to stress o Example: forearm bones in tennis players are heavier response to constant bending forces when they hit the tennis ball Absence of stress o Bone becomes weak (therefore demineralized) o Examples: prolonged bed rest, astronauts 3 Conclusion – bone is dynamic, changes depending on external environment and stress applied or lack of stress o Bone is in dynamic equilibrium with environment Hypothesized mechanism for remodeling o Hydroxyapatite crystals are piezoelectric generate a weak electric field when subjected to bending stress The weak electric field recruits bone building cells (osteoblasts) Explains thickening in forearm bone of tennis players Electric fields used as therapy for non-healing fractures Gross structure of bone different types of bone Outer wall of bone = dense, compact Inner wall of bone = porous, less dense, cancellous bone (sponge-like in appearance) o Thin rods and plates that compromise cancellous bone = trabeculae Compact bone provides strength Cancellous bone provides minimal mass solution trabeculae provides necessary support using smallest amount of material Shock absorbers o Ends of long bones are wider than shaft distributes force applied to ends of bones over larger surface – reduces force per unit area Also, cancellous bone can “give” a little to absorb shock Connective tissues Gross structure of muscles o Bundles of fibers surrounded by connective tissues Tendons 4 o Separate sheets of connective tissue (surrounding the muscles) join together at the two ends of the muscle and form the juncture with the bone o Connective tissue only o Comprised primarily of collagen (tough fibers) o Rope-like made of parallel fibers that run the length of the tendon o Only joins muscle to bone o Transmits work done by muscle to distant point Ligaments o Connective tissue that joins bone to bone, and also guides tendons by forming loops around them o Tendons and ligaments work together to redirect force exerted by muscles Moveable Joints o Allows bones to move relative to one another without undue friction o Bone articulating ends like ball and socket o Joint region surrounded by fibrous membrane (joint capsule) The fibrous membrane is continuous with the outer membrane of bone Within this membrane is the synovial membrane runs narrowly between the articulating surfaces o Synovial membrane encloses viscous fluid (synovial fluid) lubricates the joint o Ends of bones are covered with thin, smooth layer of articular cartilage (hyaline) Lubricant is needed in order to prevent friction and physical damage between bones Arthritis – loss of articular cartilage, and thus increased frictional wear between bones, resulting in growth of additional bone Weeping lubrication – During movement, the synovial fluid held in the cartilage is squeezed out mechanically to maintain a layer of fluid on the cartilage surface 5 Muscles can only contract o They contract and then exert force (pull on things) o Once contracted it can do no more work o In order to do more work some external force must be applied to stretch it o Muscles usually anchored to bone at both ends as they contract they bring the two points of attachment closer generally causes bending around the joint o Different muscles that cross the joint oppose one another so that when one contracts the other stretches o Biceps contract forearm flexes, triceps stretch o Triceps contract forearm extends, biceps stretch Opposability of muscles o triceps and biceps oppose one another in extending then flexing the forearm o Both muscles cross elbow and shoulder joints Both joints are located between the origin and insertion o Biceps angles from lateral-proximal to medial-distal in addition to flexing the forearm the biceps can also abduct the arm or supinate the forearm the action of the bicep is determined by the flexing of opposing muscles so if the bicep and tricep flex at the same time the bicep will abduct the arm, rather than flex the forearm if the palm is pronated then the biceps will contribute to supinating the forearm o Gluteus Maximus Gluteal muscles retract the hindlimb in quadrupeds (not in humans) 6 Humans have an erect, bipedal gait which means that the function of the gluteal muscles is different in humans not maximal if our gluteus maximus is narcotized we would still be able to walk 7 Vertebrate Anatomy – Biol 161A Lecture 12 – Adaptations for Life in Water High density of water allows organisms with neutral buoyancy to be support with no effort Demands on skeleton reduced fish vertebral column is an axis of locomotion rather than support Fish have no zygapophyses, instead have amphicoelus vertebrae o Both Osteichthyes and Chondrichthys Higher density causes higher viscosity thus higher resistance to movement o Because of higher viscosity there is more friction and drag on animal Three main body adaptations for life in water o Sustained, efficient locomotion best for fish in large expanses of open water (tuna, marlin, bonito) o Acceleration to catch prey o Maneuverability to forage for food, escape predators, live in habitats like coral reefs o Can only be ideally adapted to ONE of these functions (tradeoffs) most fish however are generalists and reflect a compromise between these functions Constraints on locomotion – Drag o An animal moving through a medium must move the medium itself, costing energy o Work is done by the animal to move the medium o Friction drag and pressure drag affect fish o Friction Drag Friction between flanks of fish and water As fish swims, layer of water next to it is pulled along with it at nearly same speed At some distance from the fish the water is not influenced by movement 1 Between these two regions^ is the boundary layer – the layer of water that is in some way displaced by a moving object The shearing of water within boundary layer represents friction nd requires work from the fish When fish is moving slowly and is streamlined it does not generate eddies (whirlpool type motion of water) within boundary layer this represents LAMINAR FLOW Laminar Flow Object moves slowly and is streamlined No eddies Turbulent Flow Object moves quickly and is less streamlines Generates eddies Greatly increases friction drag o Pressure Drag Caused by pressure differences generated in front of and behind the moving object Positive pressure = push generated in front of object Negative pressure = pull generated behind object Represent work being done by object o Fish can be shaped to minimize either pressure drag or friction drag (but not both) Reducing friction drag minimize lateral surface area It is the pull of the surface on the surrounding medium that generates friction less surface area results in less friction drag Results in short, stout object Will increase pressure drag because of an increase in the frontal area 2 Reduce pressure drag minimize surface area of leading and trailing faces of object Results in smallest displacement of water Long, slender object (like snake or eel) Will increase friction drag because lateral surface area is increased o Optimal shape (fusiform) is a compromise between these two forms Spindle with circular cross-section and max width equal to ¼ its length Max width is placed 1/3 of the way down the body ¼ (l) ¼ (l) Fish deviate from ideal fusiform because the cross-section is horizontally compressed (vertical axis longer than horizontal axis) Horizontally compressed because flank of body is used in propulsion, the broader flank is pushed against the water as the body generates sinusoidal waves Fish are not rigid bodies (like man-made objects propelled by engines) they require movement of some portion of body to propel through water o As they move portions of their body they generate turbulence Undulations o Most fish move with variations of sinusoidal waves that travel from head towards tail o They differ in how many waves loop through the body at one time o Long/slender eels have more than one wave propagating down the body at any given time o More often there is less than half a wave present for most fish o These waves literally push the animal through the water 3 o Can split up the force of the propulsive elements into thrust and lateral displacement The Thrust Force (F) is the only component that propels the fish t The Lateral Force (Fl is the component that moves the fish laterally There is a larger thrust component than lateral component because there is less resistance to moving forward rather than sideways Side of fish is broad and flat creates a lot of resistance to lateral displacement The lateral displacements constantly cancel each other out with each thrust since the direction of the tail is oscillating back and forth Thrust generated near tail is more powerful than thrust generated more anteriorly on body o Further out on tail you go, you get a larger angle from the main axis of the body AND a greater distance covered by the arc o The larger angle allows the thrust component of the force vector to be larger than the lateral component effective force increases and wasted force decreases o The greater distance covered means the tip of the tail accelerates more rapidly than the flank of the body Oscillation of tail means that tail comes to rest at end of each recovery stroke and accelerates to maximum at the end of the power stroke (when body is straight) F = (m)(a) o M = mass of water moved by the propulsive element o F = force applied by body of fish to the water, or force applied by water to fish (equal and opposite) Acceleration vs. sustained swimming o Accelerators To maximize thrust, maximize the depth of each propulsive element and the amplitude of the wave Deep body, medial fins enlarged lateral surface area HORIZONTALLY COMPRESSED Similar to oar or paddle 4 Increases force output for a single half stroke A sit and wait predator not adapted to sustained swimming Waits until prey is within striking distance striking distance = distance that can be covered with a single contraction ps muscles along one side of the body predator sweeps caudle peduncle through half a cycle and attacks Pike and pickerel The turbulence generated by an anterior segment creates friction and passes over more posterior segments the amount of turbulence progressively increases as you move towards the tail These fish can switch to sustained locomotion by folding up their medial fins reducing lateral surface area and thus reducing drag o Sustained swimmers The tail is the ONLY propulsive element VERTICALLY COMPRESSED A broad caudal peduncle becomes disadvantageous because: The amount of friction drag is directly proportional to surface area Friction drag is proportional to velocity Therefore caudal peduncle is narrowed so that sustained swimmers can swim at high speeds Ideal shape is to have a tapered peduncle with a tall crescent shaped tail Portion of body that undulates is restricted to rear of the fish This is because the more posterior the propulsive element, the greater percentage of the force is applied to thrust , and the faster it moves Percentage of forward thrust component is increased and percentage of lateral component is decreased Restricting movement of the caudal peduncle to a smaller, more posterior, narrower portion further reduces turbulence o This reduction in turbulence is enhanced by the scutes along the lateral margins of the peduncle and the vertical compression of the peduncle as the peduncle oscillates it presents a knife-like 5 edge to the water reduces turbulence and resistance to the lateral undulations These combination of changes makes these fish ideal for cruising at high speeds Tuna, swordfish, bonito live in open water and feed on dispersed prey However, they cannot maneuver as well as fish with other body shapes and cannot accelerate rapidly (although they move continuously) Summary o Fish adapted for acceleration generate drag and thus are poor sustained swimmers o Fish adapted for sustained swimming are poor accelerators and have poor maneuverability o Specialized sit-and-wait predators have 80% success rate But they encounter few prey o Generalists have 30-50% success rate for capturing prey o Sustained swimmers have 10-15% success rate But they encounter a much larger amount of prey o Maximum speeds – in terms of multiples of body length of fish Sustained swimmers – tuna: 20, mackerel:15 Generalists – Salmon: 8 Maneuverer – triggerfish: 3 o Sustained swimmers least maneuverable Convergence in sustained swimmers o Osteichthyes – tuna, swordfish o Chondrichthyes – some are well sustained swimmers o Reptiles in subclass Euryapsida (Ichthyosaurs) terrestrial ancestors o Mammals – Cetacea terrestrial ancestors o All have fusiform bodies, thin caudal peduncles, long narrow tails o Homologous traits = pectoral fins, and other things 6 o Nonhomologous structures = they all have caudal fins but are very different in origin and structure o In Ichthyosaurs and fish the tails are modifications of the posterior end of the vertebral column o In dolphins the vertebral column ends in the body, the tail is formed from lobes of connective tissues o Caudal fins considered analogous – not derived from same tissues o Tails of fish and Ichthyosaurs lies in vertical plane Ichthyosaurs derived from terrestrial ancestors with sprawling gaits and vertebral columns that flexed in a horizontal plane o Tails of Cetacea lies in horizontal plane Cetacea derived from ancestors with erect gait and vertebral columns that flexed in a vertical plane 7 Vertebrate Anatomy – Biol 161A Lecture 13 – Evolution of Flight Evolution of flight encouraged by : o Access to food new niche, new source of food (similar to when amphibians invaded land) o Escape from predators birds were first bipedal runners who developed gliding and then flying as an escape mechanism, [or flight may have begun with arboreal gliders] Advantages attained once flying evolved: o Access to non-food resources cliffs, trees, islands for protected nesting spots o Efficient locomotion long-distance migrations possible Allows utilization of sparsely spread resources Utilization of seasonal resources o Dispersal across barriers oceans or mountains Ex. Arctic Tern migrates from North to South Pole Note that these same advantages apply to those with erect gait and cursorial adaptations The advantages for birds however are more extreme long migrations, feeding over wide area Flight in Reptiles (happened first) o Pterosaurs may have been first vertebrae to fly Upper Triassic (220 myr) and persisted until end of Mesozoic (65 myr) Ranged from small, sparrow sized to largest of all fliers (25-45ft wingspans) No fossil record, unclear how they evolved flight Fed mainly on fish (most fossils found in marine deposits) While most fossils are found in marine environments it could be because fossils are much more likely to form there, and much less likely to form 1 in forest environments pterosaurs could have been abundant predators in other environments as well but we lack the fossils to tell Flight in Birds (happened second) o Strong evidence for dinosaur origin of birds Birds derived from Maniraptorians o Archaeopteryx – oldest fossil record of bird Debated whether or not it was capable of sustained flight o First birds that could certainly fly – 140 myr ago But the adaptation to flight must have come earlier because at 140 myr the modifications of birds represent specialization for flight (Sinoris) Flight in mammals (happened third) o Order Chiroptera o Bats made sudden appearance in early Cenozoic (50-60 myr) Little fossil record, not sure how their flight evolved What fliers and swimmers have in common o Both move through fluid medium and are subject to same types of drag o For birds profile drag = friction drag + pressure drag Fliers also have induced drag – caused by wing-tip vortex o Fusiform shape for birds They have a fusiform shape because they have contour feathers along body contour Their body itself is not actually fusiform they can have this fusiform figure from feathers because air is a less dense medium than water Long, flexible necks but seem continuous with the body because of these contour feathers o Wings – of all classes (reptiles, mammals, birds) Must have large surface area that can be flapped to generate lift and thrust 2 All of the wing structures in flying vertebrates involve modification of the forelimb but each arrived at this modification in a different way Therefore, bone elements in wing are convergent and homologous Primary modification = elongation of forelimb For all flying vertebrates the wing is a three-segmented forelimb with additional structures to enhance the surface area First two segments humerus and radius/ulna Third segment modification of wrist and hand bones o This third segment forms differently in each of the three groups Can tell flying vertebrates apart by their digits/hands Wings of birds involve ONLY THE FORELIMB Wings of bats and pterosaurs involve the FORELIMB AND HINDLIMB This is important because birds evolved more diversely ecologically because they had separate hindlimbs hindlimbs can evolve independently Birds may have feet specialized for running, swimming, or grabbing and dismembering prey This type of diversity is not seen in bats or pterosaurs because the hindlimbs are necessary for flight o Trunk In all cases the trunk is shortened, and stiffened Stiffened by enlarged series of sacral vertebrae, fusion of trunk vertebrae, broad ribs that may have overlapping processes This places center of gravity near shoulder joint, where propulsive drive originates Propulsive drive must be at center of gravity so that flapping does not make body summersault o Synsacrum- fusion of pelvic girdle, lumbar, sacral, caudal verte. o Note: Pygostyle- fused caudal vert. for feather attachment Enlarged, keeled sternum for attachment of enlarged pectoral muscles 3 Well developed in birds and pterosaurs, not so much in bats All have V shaped bones that brace the shoulder joints but they evolved convergently and you can tell because . . . Birds – have furcula (clavicles) and coracoids Pterosaurs – only have coracoids Bats – only have clavicles Note: In terrestrial animals the center of gravity is placed over the hind limbs since they are the main source of force generation in locomotion How birds fly o The air travels over a longer path on the top of the wing than under it the air on top must therefore travel faster this difference in velocities results in lower pressure above the wing and higher pressure below the wing creating a net push that lifts the bird o Induced drag – the mixing of air at different pressures at the tip of the wing o Birds wings are like an airfoil 2 ways to increase lift of airfoil: Increase camber (make it more curved) Angle it upwards (increase angle of attack) the angle being between direction of motion and tilt of wing o Limits: power stall angle the threshold where air above wing is no longer laminar but instead turbulent at this angle the object will lose lift and altitude In each case ^ enhanced lift occurs because of an increase in the path length the air must follow over the wing relative to under the wing o Lift is directly proportional to the surface area of the wing and speed 2 o Lift = v x S v = speed S = surface area o Slow flying birds greater surface area of wings and/or greater camber 4 In respect to fast flying birds Powered Flight o Power stroke and recovery stroke Configuration of wing must be different for each o Power stroke – generates lift and forward propulsion Wing is twisted so that leading edge tilts downward Force of wing on air is perpendicular to wing therefore the force vector points down and back Lift component perpendicular to direction of movement of fluid over surface of wing Thrust component perpendicular to lift o Recovery stroke – returns wing to starting point, maintains and generates lift “hind-wing” – area covered by humerus and radius/ulna o Gliding surface generates lift during power and recovery strokes o Remains horizontal during both strokes “fore-wing” – area derived from carpals and digits o Propulsive surface generates thrust o Horizontal during power stroke o Vertical during recovery stroke Aspect ratio o Ratio of length to average width o High aspect ratio = long, narrow wing o Low aspect ratio = short, broad wing Types of wings o Elliptical wing – (all purpose) low to moderate aspect ratio (3-6) 5 high camber High lift, slow to moderate speeds, good maneuverability, good for flapping flight (forest birds) o High speed flapping flight (hummingbirds) – long, narrow, (high aspect ratio, >10), high % of wing consists of hand/drive region Note that high flapping speed does not mean the animal is moving quickly o High speed gliding – (albatross, sheerwater) – b/c bird moves fast or flies in high speed wind – long and tapering, very high aspect ratio (12-20), low camber Hind wing long Fore wing short Reduction of influence of wing tip vortex o Low speed gliding – long, broad moderate aspect ratios high camber generate a lot of lift at low speeds slotted wing tips (vultures) enhance lift and reduce wing-tip vortex Birds power and recovery stroke mostly powered by ventrally located muscles o Power stroke – pectorals originate on outer edges of sternum and insert on humerus, membrane runs from furcular to coracoids o Recovery stroke – supracoracoideus muscle – ventrally located but lifts wing pulley system runs through triosseum foramen even though contractions occur on the ventral side of the bird the muscle moves the wing in the opposite direction 6 Triosseum foramen bordered by coracoid, clavicle, and scapula MAIN ACTION of the supracoracoideus muscle is to rotate the forelimb, rather than elevate it allows for folding of wings during recovery stroke Pterosaurs had a similar recovery stroke foramina in shoulder joint where tendon could pass from sternum to dorsal surface of humerus Recovery stroke often passive therefore good flyers can have a small supracoracoideus and thus a small sternum However, note that those with a large supracoracoideus and sternum may not be good flyers (chickens) but instead have fast take-off and periodic flight that is what requires powerful recovery stroke White meat in flight muscles of chicken anaerobic activity fast take-offs Dark meat in flight muscles of ducks high myoglobin content continuous, aerobic activity In some species the recovery stroke is partly powered by elastic recoil in the furcula o Power stroke causes furcular to bow, energy gets stored in downstroke, furcula springs back during recovery stroke and returns some of this energy, helping to lift wings Bats power stroke muscles on ventral side and recovery stroke muscles on dorsal side o Sternum much less keeled than birds because it is not an attachment point for muscles associated with BOTH power and recovery stroke (like it is for birds) o Enlarged area of attachment for pectoral muscles (different from birds) muscles meet at sheet of connective tissue that separates left and right halves that tug at each other when they contract Skeletons of birds o Hollow, long bones of wing o Lattice-work of internal struts (trabeculae) that give resistance to bending stress o However, total weight of bird skeleton is same as mammal of same size 7
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