Week 4: Bone Tissue
What are the two types of bone tissue, what are they composed of, where are they found?
- for structural and protective purposes, the superficial layer of a bone, surrounding the outside.
- Contain the function units of bone (osteons)
Spongy Bone: red and yellow marrow
- Red marrow: site of red blood cell production
- Yellow marrow: fat storage
- Trabeculae within marrow cavities
Define the axial vs appendicular skeleton
The axial skeleton forms the central axis of the body. It includes the bones that protect vital organs and support the head, neck, and trunk.
The appendicular skeleton consists of the limbs and the bones that attach them to the axial skeleton.
What part of cross-bridge cycling is affected in rigor mortis? (stiffening of muscles after death caused by biochemical changes in muscle fibers when ATP production stops.)
Myosin heads bind to actin, forming cross-bridges.
However, since there is no ATP available, the myosin heads cannot detach from actin after the power stroke.
Permanent Cross-Bridge Attachment
Without ATP, cross-bridge detachment cannot occur.
The result is a sustained contraction — the muscles become stiff and rigid
Name the joints of the elbow. What kind of joints are they, and what type of movement do they allow?
Humeroulnar Joint: Articulation between the trochlea of the humerus and the trochlear notch of the ulna. Hinge joint (a type of synovial joint: Uniaxial)
Humeroradial Joint: Articulation between the capitulum of the humerus and the head of the radius.
Gliding/hinge-type synovial joint.
Proximal Radioulnar Joint: Articulation between the head of the radius and the radial notch of the ulna.
Pivot joint (synovial: )
Explain the pathophysiology of osteoporosis. How do changes in osteoblast and osteoclast activity contribute to decreased bone density?
In osteoporosis, osteoclastic activity exceeds osteoblastic activity, resulting in net bone loss. Osteoclasts become more active or more numerous, and Osteoblast number and activity decrease with age.
Older women: Estrogen deficiency (especially postmenopausal) increases osteoclast activity and reduces osteoblast lifespan.
This weakened bone is more susceptible to fractures,
Compare and contrast osteoblasts and osteoclasts. What are their roles in bone remodeling
Osteoblasts: the bone builders!! Build a bone matrix using, may use calcium from the blood, when blood calcium levels are high.
- Some osteoblasts become embedded and differentiate into osteocytes.
Osteoclasts: the bone cleaver/crusher! May break down bone when blood calcium levels are low.
The atlas (cervical vertebra 1) causes ________.
head and neck flextion and extension
What is the physiological significance of the length-tension relationship in skeletal muscle fibers?
The length–tension relationship describes how the initial length of a muscle fiber (or sarcomere) affects the amount of tension (force) it can produce during contraction.
The tension a muscle fiber generates depends on the degree of overlap between actin (thin) and myosin (thick) filaments within its sarcomeres.
Optimal tension is produced when there is an ideal overlap—enough cross-bridges can form, but the filaments are not overly compressed or overstretched.
What characteristics do all synovial joints have in common?
All synovial joints contain articular cartilage, a joint cavity, an articular capsule, synovial fluid, and reinforcing ligaments, with associated nerves and blood vessels.
How does botulism affect neuromuscular transmission
Normally, ACh release binds to receptors on the muscle fiber membrane, triggering muscle contraction.
Botulinum toxin prevents ACh release, so the muscle fiber cannot depolarize.
Result: No action potential is generated in the muscle, and contraction fails.
Explain the units that make up the osteons, and how osteons structure support bone.
Central (Haversian) Canal: Runs longitudinally through the osteon.Contains blood vessels, lymphatics, and nerves that nourish bone cells.
Concentric Lamellae: Rings of calcified matrix arranged around the central canal.
Each lamella has collagen fibers oriented in alternating directions → gives resistance to twisting (torsional stress).
Lacunae: Small spaces between lamellae that house osteocytes (mature bone cells).
Canaliculi: Tiny channels radiating from each lacuna. Allow nutrient, waste, and signaling exchange between osteocytes and blood vessels in the central canal
Describe the difference between the female and male pelvis. Why is this important?
The female pelvis is wider, more rounded, with a larger pelvic outlet to support pregnancy and childbirth.
The male pelvis is narrower and deeper to support more weight and optimized for strength and locomotion, as opposed to childbirth
The following is a list of events that take place at the neuromuscular junction.
1. Acetylcholine binds to receptors on the motor end plate (sarcolemma).
2. The nerve impulse arrives at the axon terminal.
3. Acetylcholine diffuses across the synaptic cleft.
4. Vesicles at the axon terminal release acetylcholine in the synaptic cleft.
5. An electrical message is started on the muscle cell membrane.
2, 4, 3, 1, 5.
Describe the muscles that allow the elbow to flex and extend (what are the antagonists, agonist and syngergist)
Flexion:
Agonists (prime movers): Biceps brachii, brachialis, brachioradialis:
Antagonists: Triceps
Syngergist: upper back
Extention:
Agonist: Triceps
Antagonist: biceps brachii, brachialis, brachioradialis
Synergist: aconeus
Damage to what ligament would result in varus and valgus deformities
MCL protects against valgus stress → damage causes valgus deformity.
LCL protects against varus stress → damage causes varus deformity.
Explain the negative feedback loops for Hypercalcemia and Hypocalcemia
Cervical vertebrae are easily distinguished from the other vertebrae by the presence of:
transverse foramina
Suppose that a toxin released during a bacterial infection causes the sarcoplasmic reticulum to become
incapable of removing calcium from the sarcoplasm. Assuming the muscle cells have plenty of ATP, what would you
expect to see as a result from this infection?
Constant contraction of skeletal muscles, without relaxation phases.
Explain the different types of levers, give an example for each.
First-Class: Fulcrum between effort (applied force) & load (resitive force)
Effort – Fulcrum – Load (neck extension)
Second-Class: Load between fulcrum & effort
Fulcrum – Load – Effort (calf raise)
Third-Class: Effort between fulcrum & load
Fulcrum – Effort – Load (Bicept curl)
Explain the difference between aerobic and anerobic respiration
Aerobic: Efficient, oxygen-dependent, supports endurance: Slow-twitch muscle fibers, red
Anaerobic: Fast, inefficient, oxygen-independent, supports short, high-intensity efforts, but produces fatigue-causing byproducts such as lactic acid: Fast-twitch muscle fibers, white
Describe the sequence of events in endochondral ossification, beginning with the cartilage model and ending with the formation of secondary ossification centers.
1. Development of the Hyaline Cartilage Model (from mesenchymal stem cells)
2. Growth of the Cartilage Model (matrix begins to calcify)
3. Development of the Primary Ossification Center:
4. Development of the Medullary (Marrow) Cavity
5.Development of the Secondary Ossification Centers
6. Formation of Articular Cartilage and Epiphyseal Plate
What are the types of bone (shape) and give examples of them.
Long Bones: Longer than they are wide; have a shaft (diaphysis) and two ends (epiphyses).
Designed primarily for movement and support (femur, humerus radius etc.)
Short Bones: Roughly cube-shaped; they provide support and stability with little movement.
Mostly spongy bone covered by a thin layer of compact bone. (Carpals, tarsals)
Flat bones: Provide protection and broad surfaces for muscle attachment. (skull, sternum)
Irregular: Complex shapes that do not fit into other categories. Anchor points for muscles (vertebrae, some facial bones)
Sesamoid: Small, round bones that protect tendons and improve mechanical leverage. (patella)
List the steps of cross-bridge cycling
The binding of calcium to troponin
ATP hydrolysis
Myosin binds actin
Release of inorganic phosphate
Power stroke
Replacement of spent ADP with new ATP
Myosin releases actin
Explain the types of muscle action:
Isotonic Muscle Actions
Definition: Muscle changes length while producing force; movement occurs at a joint.
Two Subtypes:
Concentric Contraction
Muscle shortens while generating force.
Example: Biceps brachii shortening during a bicep curl (lifting the weight).
Eccentric Contraction: Muscle lengthens while generating force. Example: Biceps brachii lengthening while slowly lowering a dumbbell in a bicep curl.
Isometric Muscle Action
Definition: Muscle produces force without changing length; joint angle remains the same.
Example: Holding a plank, wall sit, or holding a weight in a fixed position.
Explain how intramembranous ossification contributes to the growth and development of the flat bones of the skull. Why is this process important during fetal development?
Intramembranous ossification allows the rapid expansion of cranial bones, accommodating the growing brain during fetal and early postnatal development.
The skull sutures remain flexible, permitting skull deformation during birth and continued growth after birth.
Provides protection for the brain while still allowing the cranial vault to enlarge as the brain develops.