Structural Support and Movement Chapter 36 Part 1

Impacts, Issues Pumping Up Muscles Increasing muscle size and strength with drugs such as “andro” has unwanted side effects and can damage other organ systems

36.1 Invertebrate Skeletons Hydrostatic skeleton An enclosed fluid that contracting muscles act upon (as in sea anemones, earthworms) Exoskeleton A hardened external skeleton found in some mollusks and all arthropods Endoskeleton An internal skeleton, as in echinoderms

Hydrostatic Skeleton: Sea Anemone

mouth gastro-vascular cavity; the mouth can close and trap fluid inside this cavity Figure 36.2 Hydrostatic skeleton of a sea anemone. (a) Water is drawn into the gastrovascular cavity through the mouth. When the cavity is filled and mouth is closed, muscles can act on the trapped fluid and alter body shape. There are two sets of muscles: circular muscles ring the body; longitudinal ones run the length of the body. (b) One anemone inflated with water (left) and another that has expelled water from the gastrovascular cavity and pulled in its tentacles (right). Fig. 36-2a, p. 618

Animation: Hydrostatic skeleton

Hydrostatic Skeleton: Earthworm

Exoskeleton: Fly

vertical muscle relaxes vertical muscle contracts thorax longitudinal muscle contracts longitudinal muscle relaxes vertical muscle relaxes vertical muscle contracts Figure 36.4 Fly wing movement. Wings attach to the thorax at pivot points. When muscles inside the thorax contract and relax, the thorax changes shape and the wings pivot up and down at their attachment point. A Wings pivot down as the relaxation of vertical muscle and the contraction of longitudinal muscle pulls in sides of thorax. B Wings pivot up when the contraction of vertical muscle and relaxation of longitudinal muscle flattens the thorax. Fig. 36-4, p. 619

Animation: Fly wing action

Exoskeleton: Spider

36.1 Key Concepts Invertebrate Skeletons Contractile force exerted against a skeleton moves animal bodies In many invertebrates a fluid-filled body cavity is a hydrostatic skeleton Others have an exoskeleton of hard structures at the body surface Still others have a hard internal skeleton, or endoskeleton

36.2 The Vertebrate Endoskeleton All vertebrates have an endoskeleton Usually consists primarily of bones Supports the body, site of muscle attachment Protects the spinal cord The vertebral column (backbone) is made up of individual vertebrae separated by intervertebral disks made of cartilage

Axial and Appendicular Skeleton Axial skeleton Skull Vertebral column Ribs Appendicular skeleton Pectoral girdle Pelvic girdle Limbs

Skeletal Elements: Fish and Reptile

vertebral column pectoral girdle pelvic girdle Figure 36.7 Skeletal elements typical of (a) a cartilaginous fish and (b) an early reptile. Compare Figures 26.12, 26.22, and 26.31. pelvic girdle Fig. 36-7a, p. 620

vertebral column skull bones rib cage pelvic girdle pectoral girdle Figure 36.7 Skeletal elements typical of (a) a cartilaginous fish and (b) an early reptile. Compare Figures 26.12, 26.22, and 26.31. Fig. 36-7b, p. 620

The Human Skeleton Some features of the human skeleton are adaptations to upright posture and walking Foramen magnum at the base of the skull allows brain and spinal cord to connect Vertebrae stacked one above the other in an S curve

Bones of the Human Skeleton

CLAVICLE (collarbone) A Skull bones CRANIAL BONES FACIAL BONES D Pectoral girdle and upper limb bones CLAVICLE (collarbone) B Rib cage SCAPULA (shoulder blade) STERNUM (breastbone) HUMERUS (upper arm bone) RIBS (twelve pairs) RADIUS (forearm bone) C Vertebral column, or backbone ULNA (forearm bone) CARPALS (wrist bones) VERTEBRAE 1 2 3 4 5 INTERVERTEBRAL DISKS PHALANGES (thumb, finger bones) METACARPALS (palm bones) E Pelvic girdle and lower limb bones PELVIC GIRDLE (six fused bones) FEMUR (thighbone) Figure 36.8 Bone (tan) and cartilage (light blue) elements of the human skeleton. Left, labels for the axial portion, and (right) for the appendicular portion. PATELLA (kneebone) ligament bridging a knee joint, side view, midsection TIBIA (lower leg bone) FIBULA (lower leg bone) TARSALS (ankle bones) METATARSALS (sole bones) PHALANGES (toe bones) Fig. 36-8, p. 621

Animation: Human skeletal system

36.3 Bone Structure and Function Bones have a variety of shapes and sizes Long bones (arms and legs) Flat bones (skull, ribs) Short bones (carpals) The human skeleton has 206 bones ranging from tiny ear bones to the massive femur

Bone Anatomy Bones consist of three types of living cells in a secreted extracellular matrix Osteoblasts build bones Osteocytes are mature osteoblasts Osteoclasts break down bone matrix Bone cavities contain bone marrow Red marrow in spongy bone forms blood cells Yellow marrow in long bones is mostly fat

Bone Anatomy: Long Bone

Figure 36.9 (a) Structure of a human femur, or thighbone, and (b) a section through its spongy and compact bone tissues. Fig. 36-9a, p. 622

space occupied by living bone cell blood vessel nutrient canal location of yellow marrow Figure 36.9 (a) Structure of a human femur, or thighbone, and (b) a section through its spongy and compact bone tissues. compact bone tissue spongy bone tissue 55 µm Fig. 36-9a, p. 622

Figure 36.9 (a) Structure of a human femur, or thighbone, and (b) a section through its spongy and compact bone tissues. Fig. 36-9b, p. 622

of dense connective tissue spongy bone tissue Figure 36.9 (a) Structure of a human femur, or thighbone, and (b) a section through its spongy and compact bone tissues. compact bone tissue outer layer of dense connective tissue blood vessel Fig. 36-9b, p. 622

Animation: Structure of a femur

Bone Functions

Bone Formation and Remodeling The embryonic skeleton consists of cartilage which is modeled into bone, grows until early adulthood, and is constantly remodeled Bones and teeth store the body’s calcium Calcitonin slows release of calcium from bones Parathyroid hormone releases bone calcium Sex hormones encourage bone building Cortisol slows bone building

Long Bone Formation

Embryo: cartilage model of bone forms Fetus: blood vessel invades model; osteoblasts start producing bone tissue; marrow cavity forms Newborn: remodeling and growth continue; secondary bone-forming centers appear at knobby ends of bone Figure 36.10 Long bone formation, starting with osteoblast activity in a cartilage model formed earlier in the embryo. The bone-forming cells are active first in the shaft region, then at the knobby ends. In time, cartilage is left only at the ends. Adult: mature bone Fig. 36-10, p. 623

About Osteoporosis Osteoporosis (“porous bones”) When more calcium is removed from bone than is deposited, bone become brittle and break easily Proper diet and exercise help keep bones healthy

Osteoporosis

36.4 Skeletal Joints—Where Bones Meet Area of contact or near contact between bones Three types of joints Fibrous joints (teeth sockets): no movement Cartilaginous joints (vertebrae): little movement Synovial joints (knee): much movement

Synovial Joints In synovial joints, bones are separated by a fluid-filled cavity, padded with cartilage, and held together by dense connective tissue (ligaments) Different synovial joints have different movements Ball-and-socket joints (shoulder) Gliding joints (wrist and ankles) Hinged joints (elbows and knees)

Three Types of Joints

Three Types of Joints

fibrous joint attaches tooth to jawbone synovial joint (ball and socket) between humerus and scapula cartilaginous joint between rib and sternum cartilaginous joint between adjacent vertebrae synovial joint (hinge type) between humerus and radius Figure 36.12 (a) Examples of the three types of joints. (b) Simplified diagram of the structure of the left knee with muscles stripped away. Several ligaments attach the femur to the tibia and chunks of cartilage called menisci help keep the bones properly aligned. Compare the photo in Figure 36.8. synovial joint (ball and socket) between pelvic girdle and femur Fig. 36-12a, p. 624

femur patella cartilage ligaments menisci tibia fibula Figure 36.12 (a) Examples of the three types of joints. (b) Simplified diagram of the structure of the left knee with muscles stripped away. Several ligaments attach the femur to the tibia and chunks of cartilage called menisci help keep the bones properly aligned. Compare the photo in Figure 36.8. tibia fibula Fig. 36-12b, p. 624

36.5 Those Aching Joints We ask a lot of our joints when we engage in sports, carry out repetitive tasks, or strap on a pair of high heels

Joint Injuries and Diseases Common joint injuries Sprained ankle; torn cruciate ligaments in knee; torn meniscus in knee; dislocations Arthritis (chronic inflammation) Osteoarthritis; rheumatoid arthritis; gout Bursitis (inflammation of a bursa)

36.2-36.5 Key Concepts Vertebrate Skeletons Vertebrates have an endoskeleton of cartilage, bone, or both Bones interact with muscles to move the body; they also protect and support organs, and store minerals Blood cells form in some bones A joint is a place where bones meet; there are several kinds

36.6 Skeletal–Muscular Systems Muscle fibers Long, cylindrical cells with multiple nuclei that hold contractile filaments Tendons attach skeletal muscle to bone Muscle contraction transmits force to bone and makes it move Muscles and bones interact as a lever system Many skeletal muscles work in opposing pairs

Skeletal–Muscular Action

C The first muscle group in the upper hindlimb contracts again and draws it back toward body. B An opposing muscle group attached to the limb forcefully contracts and pulls it back. The contractile force, applied against the rock, now propels the frog forward. Figure 36.14 A frog on a rock demonstrating how small contractions and the action of opposing muscles can cause big movements. A A muscle attached to each upper hindlimb contracts and pulls it slightly forward relative to main body axis. Fig. 36-14, p. 626

Opposing Muscle Groups

Triceps contracts, pulls the forelimb down. Triceps relaxes. Triceps contracts, pulls the forelimb down. Biceps contracts at the same time, and pulls forelimb up. At the same time, biceps relaxes. Figure 36.15 Two opposing muscle groups in human arms. A When the triceps relaxes and its opposing partner (biceps) contracts, the elbow joint flexes and the forearm is pulled upward. B When the triceps contracts and the biceps relaxes, the forearm is extended downward. Fig. 36-15, p. 626

Animation: Opposing muscle action

Muscles and Tendons

Muscles and Tendons

Straightens the forearm at elbow TRICEPS BRACHII Straightens the forearm at elbow BICEPS BRACHII PECTORALIS MAJOR Bends the forearm at the elbow Draws the arm forward and in toward the body DELTOID SERRATUS ANTERIOR Raises the arm Draws shoulder blade forward, helps raise arm, assists in pushes TRAPEZIUS Lifts the shoulder blade, braces the shoulder, draws the head back EXTERNAL OBLIQUE Compresses the abdomen, assists in lateral rotation of the torso LATISSIMUS DORSI Rotates and draws the arm backward and toward the body RECTUS ABDOMINIS Depresses the thoracic (chest) cavity, compresses the abdomen, bends the backbone GLUTEUS MAXIMUS Extends and rotates the thigh outward when walking, running, and climbing ADDUCTOR LONGUS Flexes, laterally rotates, and draws the thighs toward the body BICEPS FEMORIS Figure 36.16 (a) Muscles of the human musculoskeletal system. These are the skeletal muscles that gym enthusiasts are familiar with; many more are not shown. Also labeled is the Achilles tendon, the largest tendon in the body and the most frequently injured. It attaches muscles in the calf to the heel bone. (b) Tendons at a synovial joint. Bursae form between tendons and bones or some other structure. These fluid-filled sacs help reduce friction between adjacent tissues. (Hamstring muscle) Draws thigh backward, bends the knee SARTORIUS Bends the thigh at the hip, bends lower leg at the knee, rotates the thigh in an outward direction GASTROCNEMIUS Bends the lower leg at the knee when walking, extends the foot when jumping QUADRICEPS FEMORIS Set of four muscles that flex the thigh at the hip, extend the leg at knee Achilles tendon TIBIALIS ANTERIOR Flexes the foot toward the shin Fig. 36-16a, p. 627

muscle tendon bursae synovial cavity Figure 36.16 (a) Muscles of the human musculoskeletal system. These are the skeletal muscles that gym enthusiasts are familiar with; many more are not shown. Also labeled is the Achilles tendon, the largest tendon in the body and the most frequently injured. It attaches muscles in the calf to the heel bone. (b) Tendons at a synovial joint. Bursae form between tendons and bones or some other structure. These fluid-filled sacs help reduce friction between adjacent tissues. synovial cavity Fig. 36-16b, p. 627

Animation: Human skeletal muscles

36.6 Key Concepts The Muscle–Bone Partnership Skeletal muscles are bundles of muscle fibers that interact with bones and with one another Some cause movements by working as pairs or groups; others oppose or reverse the action of a partner muscle Tendons attach skeletal muscles to bones

Animation: Long bone formation

Animation: Vertebrate skeletons