Bones, Muscles and Joints Honor

Science & Health

Requirements

1. What is the difference between an endoskeleton and an exoskeleton? Which of these types of skeleton do humans have?

   Answer: An endoskeleton is the skeleton INTERNAL to the body (formed by bones and cartilage within the organism, covered by soft tissues); present in vertebrates (fish, amphibians, reptiles, birds and mammals). An exoskeleton is the EXTERNAL skeleton, a rigid shell that surrounds and protects the body from the outside; present in arthropods (insects, spiders, crustaceans) and mollusks. Humans, being vertebrates, have an ENDOSKELETON (internal skeleton), which grows along with the body and does not need to be replaced. — The advantage of the endoskeleton is continuous growth (no need to be replaced like in arthropods); the advantage of the exoskeleton is external mechanical protection, but it requires ecdysis (molting) to grow. Vertebrates with endoskeletons are generally larger — an exoskeleton would be too heavy in large bodies.

2. Cite at least three functions of the skeletal system.

   Answer: Pelo menos três funções do sistema esquelético: (1) Sustentação - dá forma e estrutura ao corpo, suportando o peso de tecidos e órgãos; (2) Proteção de órgãos vitais - o crânio protege o cérebro, as costelas protegem coração e pulmões, a coluna protege a medula espinhal; (3) Movimento - os ossos servem de alavanca para os músculos, permitindo a locomoção. Outras: produção de células sanguíneas (hematopoiese, na medula óssea vermelha) e reserva de minerais (cálcio e fósforo). — Red bone marrow (present in flat bones such as the sternum and hip) produces about 200 billion red blood cells per day throughout life; the calcium stored in the bones (about 99% of the body's total) is mobilized when the blood needs it, hence the importance of adequate calcium intake in the diet to prevent osteoporosis.

3. Describe:
   • Axial skeleton
   • Appendicular skeleton

   Answer: 1) Axial skeleton: forms the central axis of the body — skull, vertebral column, ribs and sternum (in addition to the hyoid bone). It supports the head and trunk and protects vital organs such as the brain, spinal cord, heart and lungs. 2) Appendicular skeleton: formed by the limbs and their attachment girdles — the pectoral girdle (scapula and clavicle) with the upper limbs (arm, forearm and hand) and the pelvic girdle with the lower limbs (thigh, leg and foot). It is responsible for locomotion and the movements of the body. — Dividing the skeleton into axial (axis and protection) and appendicular (limbs and movement) is the first step to understanding how the body supports itself and moves.

4. Describe the classification of bones according to their shape, illustrating them.

   Answer: Bones are classified by shape into: (1) Long — length greater than width, with a diaphysis (body) and two epiphyses (ends): femur, humerus, tibia, fibula, radius, ulna. (2) Short — similar length, width and height (cube-shaped): bones of the carpus (wrist) and tarsus (ankle). (3) Flat — thin and flattened, with a protective function: bones of the skull, scapula, sternum, ribs. (4) Irregular — complex shape that does not fit into the other categories: vertebrae, hip bone (ilium), some bones of the face. (5) Sesamoid — small, develop within tendons at points of friction: the patella (knee) is the largest. Illustrate each type. — Classification by shape is traditional since the anatomist Andreas Vesalius (1543); long bones are levers for movement; flat bones protect; short bones absorb impact; irregular bones are functional (vertebrae support the spine); sesamoid bones protect tendons at points of friction (the patella is the largest sesamoid bone in the body).

5. How many bones does an adult human have?

   Answer: An adult human has 206 bones. Babies are born with approximately 270 bones, but during growth some fuse together (especially those of the skull, the sacrum and the coccyx), reducing the final number in adulthood. The distribution: 22 in the skull (8 cranial + 14 facial), 6 in the ears (3 in each), 1 hyoid, 26 vertebral column, 25 thoracic cage (sternum + ribs), 64 upper limbs (girdle + arms + hands), 62 lower limbs (girdle + legs + feet). — The reduction from 270 to 206 bones occurs mainly through the fusion of plates in the skull (fontanelles that close by 18 months), in the sacrum (5 sacral vertebrae that fuse) and in the coccyx (4-5 coccygeal vertebrae). Individual variations exist (some people have extra ribs or additional vertebrae), but 206 is the standard average number.

6. Draw or paste a figure of a skeleton, identifying at least 25 bones, without repeating them.

   Answer: Monte a figura do esqueleto e identifique ao menos 25 ossos diferentes, sem repetir. Exemplo de 25 ossos do corpo humano: (1) frontal; (2) parietal; (3) temporal; (4) occipital; (5) mandíbula; (6) maxila; (7) clavícula; (8) escápula (omoplata); (9) esterno; (10) costelas; (11) vértebras (coluna); (12) úmero; (13) rádio; (14) ulna (cúbito); (15) carpo (ossos do punho); (16) metacarpos; (17) falanges da mão; (18) ílio (osso do quadril); (19) fêmur; (20) patela (rótula); (21) tíbia; (22) fíbula (perônio); (23) tarso (ossos do tornozelo); (24) metatarsos; (25) falanges do pé. — Suggested 25 bones to identify: frontal, parietal, occipital, mandible, clavicle, sternum, rib, scapula, humerus, radius, ulna, phalanges (hand), vertebrae, ilium, sacrum, femur, patella, tibia, fibula, calcaneus, talus, metatarsal, phalanges (foot), zygomatic, maxilla — covering skull, trunk and limbs.

7. Describe the structure and development of the skeleton. Define diaphysis, metaphysis and epiphysis, illustrating them.

   Answer: The skeleton is formed by bones made of mineralized matrix (calcium + collagen) and develops from cartilage (endochondral ossification) or membrane (intramembranous). Diaphysis: central body of the long bone. Metaphysis: transition zone. Epiphysis: rounded ends that articulate. — Endochondral ossification is responsible for 90% of the bones (long, short, irregular); intramembranous ossification forms the flat bones of the skull. The diaphysis concentrates the yellow marrow; the metaphysis houses the epiphyseal disc (growth plate); the epiphysis has articular cartilage. Add an illustrative drawing.

8. What is the epiphyseal plate (growth plate) and what is its importance?

   Answer: The epiphyseal disc (growth plate) is the cartilaginous layer between the diaphysis and the epiphysis of long bones where longitudinal growth occurs. Its importance is to determine the individual's final height, closing between 18 and 25 years of age with complete skeletal maturation. — The closure of the plates is influenced by hormones (estrogen accelerates closure — which is why women stop growing earlier); fractures in the epiphyseal disc in children can compromise future growth. Wrist X-rays are used to estimate pediatric bone age and predict final height.

9. What are joints? Describe their 3 classes with their subdivisions, illustrating all of them.

   Answer: Joints are unions between bones. The 3 classes: fibrous (no movement — skull sutures, syndesmoses, gomphoses); cartilaginous (little movement — synchondroses, symphyses such as the pubic); synovial (wide movement — ball-and-socket, hinge, pivot, ellipsoid, saddle, plane). — Synovial joints have a capsule, synovial fluid (lubrication), articular cartilage and sometimes menisci (knee); they are the most mobile and the most prone to injury. The pubic symphysis connects the hip bones and becomes flexible during childbirth. Add drawings illustrating each subdivision.

10. Make a model of one of the 6 synovial joints.

    Answer: Build a model (out of modeling clay, cardboard, EVA foam or articulated parts) of one of the 6 synovial joints: ball-and-socket (shoulder/hip), hinge (elbow/knee), pivot (atlas-axis), ellipsoid (wrist), saddle (thumb) or plane (carpus). Present it to the instructor. — The ball-and-socket joint allows movement in 3 axes (most mobile); the hinge is uniaxial in flexion-extension (elbow); the pivot allows rotation (atlas-axis in the neck rotates the head); the ellipsoid allows 2 axes (wrist); the saddle is specific to the thumb; the plane, minimal sliding.

11. What is a bone fracture? How is the medical correction performed? Describe the following types, illustrating them: external (open) and internal; transverse, oblique and spiral; complete and incomplete; comminuted and greenstick.

    Answer: A bone fracture is the total or partial break in the continuity of a bone, generally caused by trauma, a fall or excessive effort. Medical correction: 1) reduction (realigning the fragments into place, closed or surgical); 2) immobilization (cast, splint, or internal fixation with plates/pins/screws); 3) rehabilitation (physical therapy to recover strength and movement). Types: 1) OPEN (external): the bone breaks through the skin and is exposed to the environment, with a high risk of infection. 2) INTERNAL (closed): the bone breaks but the skin remains intact. 3) TRANSVERSE: the fracture line is straight and perpendicular to the long axis of the bone. 4) OBLIQUE: the fracture line is diagonal/slanted relative to the bone's axis. 5) SPIRAL: the fracture line is helical (twisting), caused by rotational trauma. 6) COMPLETE: the bone breaks entirely, separating into two or more fragments. 7) INCOMPLETE: the bone cracks partially without completely separating. 8) COMMINUTED: the bone fragments into several pieces (more than two). 9) GREENSTICK: an incomplete fracture typical of children — the bone bends and cracks on only one side, like a green branch that bends without snapping. Illustrate each type with a drawing. — An open fracture is an emergency (risk of infection); a greenstick fracture only occurs in children because their bones have more collagen and bend before breaking completely; a comminuted fracture generally requires surgery with plates/screws. Average bone healing time: 6-8 weeks in adults; faster in children.

12. Draw or paste pictures of a vertebral column, know how to divide it into its 5 regions and state how many vertebrae make up each one.

    Answer: The vertebral column has 5 regions: cervical (7 vertebrae, neck); thoracic (12, articulated with ribs); lumbar (5, lower back); sacral (5 fused, form the sacrum); coccygeal (4-5 fused, coccyx). Total: 33 vertebrae at birth, 26 in the adult after the fusions. — The mnemonic rule '7-12-5-5-4' helps to memorize it (cervical-thoracic-lumbar-sacral-coccygeal); the spine has natural curvatures (cervical and lumbar lordosis, thoracic and sacral kyphosis) that distribute weight. C1 (atlas) supports the skull; C2 (axis) allows rotation of the head.

13. What is osteoporosis? What are the most common fracture sites? What is the risk age? Who is the most affected group? What is the best test to detect it? List 5 measures that help prevent osteoporosis.

    Answer: 1) What osteoporosis is: a disease that reduces bone density and mass, leaving the bones porous, fragile and prone to fractures. 2) Most common fracture sites: hip (femoral neck), vertebral column (vertebrae) and wrist. 3) Risk age: mainly after age 50. 4) Most affected group: postmenopausal women (the drop in estrogen accelerates bone loss). 5) Best test to detect it: bone densitometry (DEXA). 6) Five measures that help prevent it: (a) adequate calcium intake (milk and dairy products, dark green vegetables); (b) vitamin D (sun exposure and diet); (c) regular physical exercise, especially strength and impact exercises; (d) avoiding smoking and alcohol; (e) avoiding falls and maintaining a healthy weight. — The drop in estrogen at menopause accelerates bone loss — which is why women are more affected; bone densitometry (DXA) measures grams of mineral per cm² of the lumbar spine and femur; the WHO defines osteoporosis as a T-score ≤ -2.5. Vitamin D is essential for calcium absorption (morning sun helps).

14. What are the main functions of muscles?

    Answer: Functions of the muscles: body movement (locomotion, speech, chewing), postural maintenance, heat production (thermogenesis), protection of internal organs and blood pumping (cardiac muscle). They work with the skeleton, forming the musculoskeletal system. — The muscles account for about 40% of body weight and generate about 85% of body heat at rest through the metabolism of muscle fibers; shivering is the body's automatic response to generate extra heat (involuntary contractions). The heart beats about 100,000 times a day, without stopping.

15. Describe, giving at least 3 examples of each one (if any):
    • Skeletal striated muscle
    • Cardiac striated muscle
    • Smooth muscle

    Answer: 1) Striated skeletal muscle: voluntary contraction, attached to the bones and responsible for locomotion and posture. Examples: biceps, quadriceps, gastrocnemius, pectoral and deltoid. 2) Striated cardiac muscle: involuntary and exclusive to the heart, forming the myocardium. Examples of location: wall of the right and left atria and wall of the right and left ventricles. 3) Smooth muscle: involuntary, present in the walls of internal organs. Examples: intestine, stomach, blood vessels, uterus and bladder. — Striated muscles have a striped appearance under the microscope (aligned parallel fibers); cardiac muscle has mononuclear cells with intercalated discs for electrical conduction; smooth muscle has mononuclear spindle-shaped cells. The skeletal muscle tires quickly; the cardiac cannot stop; the smooth is resistant to fatigue.

16. Identify the following muscles: masseter, trapezius, deltoid, pectoralis major, biceps, quadriceps, triceps, rectus abdominis, serratus anterior, gluteus maximus, latissimus dorsi, gastrocnemius and soleus.

    Answer: Identify on the body or in a picture each muscle: masseter (jaw), trapezius (shoulders), deltoid (shoulder), pectoralis major (chest), biceps/triceps (arm), rectus abdominis (abdomen), serratus anterior, quadriceps (thigh), gluteus maximus, latissimus dorsi (back), gastrocnemius and soleus (calf). — The biceps flexes the elbow (anterior part), the triceps extends it (posterior); the quadriceps has 4 heads (vastus medialis, lateralis, intermedius and rectus femoris); the gastrocnemius (superficial, with 2 heads) and the soleus (deep) form the triceps surae; the gluteus maximus is the largest muscle in the human body.

17. Describe the mechanism of muscle contraction.

    Answer: Muscle contraction: a nerve impulse releases calcium into the sarcoplasm; calcium exposes active sites on the actin; myosin (with ATP) pulls the actin filaments, shortening the sarcomere. When the stimulus ceases, calcium is taken back up and the muscle relaxes. This is the sliding filament model (Huxley, 1954). — Each sarcomere (contractile unit) has thin filaments (actin) and thick ones (myosin); ATP is the energy of contraction — its absence causes rigor mortis after death. Duchenne disease affects the protein dystrophin, compromising the sarcomere; strength training increases the number of myofibrils, hypertrophying the muscle.

18. Describe the difference between voluntary muscles and involuntary muscles.

    Answer: Voluntary muscles respond to the conscious command of the brain (striated skeletal — biceps, quadriceps, pectoral); they are used for intentional movements such as walking, speaking, writing. Involuntary muscles work automatically, without conscious control (cardiac in the heart; smooth in the intestine, stomach, blood vessels). — Voluntary muscles are controlled by the somatic nervous system (motor cortex → spinal nerves → muscle); involuntary muscles, by the autonomic nervous system (sympathetic and parasympathetic). It is possible to partially train involuntary muscles (yoga, biofeedback), but the control is never as total as with voluntary muscles.

19. Find at least three Bible verses that mention muscles, bones or joints.

    Answer: Three examples: Genesis 2:23 — 'bone of my bones, flesh of my flesh'; Psalm 22:14 — 'all my bones are out of joint'; Ezekiel 37:1-14 — vision of the dry bones in the valley being resurrected. Others: Proverbs 3:8 (refreshment to the bones), Job 10:11 (you knit me together with bones and sinews). — Ezekiel 37 is a key Adventist text about the literal and symbolic resurrection of Israel; Psalm 22:14 is messianic, describing the crucifixion hundreds of years in advance (joint dislocation does actually occur in crucified people); Genesis 2:23 establishes the unity of man and woman in creation.