Skeletal system (objective 13-16) and Muscular system

What are paranasal sinuses, where are they located and what do they do?

what they are: Hollow, air-filled pockets inside specific skull bones lined with thin membranes.

where they are (4 skull bones): 1. frontal (forehead area) 2. sphenoid( deep behind your eyes) 3. Ethmoid (between eyes and nose 4. Maxillary( cheekbones)

what they do: 1. Lighten your heavy skull. 2. Warm, filter, and moisten air you breathe. 3. Give your voice a fuller sound (resonance).

What makes up the spine, why do we have it, and what are normal vs. abnormal curves?

Components (33 bones in sections): 7 cervical (neck), 12 thoracic (mid-back/ribs) 5 lumbar (lower back) 1 sacrum ( 5 fused bones) 1 coccyx (3-4 fused tailbone)

Purpose: holds your body weight upright and protects your spinal cord inside a hollow bony tunnel.

Normal curves: lordosis( inward curve): neck and lower back (develops as baby learns to sit/ walk). Kyphosis (outward curve): mid-back and sacrum (born with these).

Abnormal curves: Scoliosis: side to side curve (s-shaped spine) Exaggerated Kyphosis: hunchback (overly rounded upper back). exaggerated Lordosis: Sway back (deep inward curve in lower back).

What parts are on a basic vertebra and hole do neck mid-back, and lower-back vertebrae look different?

Basic vertebra parts:

Body: thick front block carrying weight.

Vertebral foramen: center hole for spinal cord.

Spinous process: back bump sticking straight out (the bumps you feel along your spine)

Transverse Processes: side bumps sticking out to left and right.

Regional Differences:

Cervical (neck/C1-C7); smallest; split (bifid) back bumps; extra side holes(transverse foramina) for beck blood vessels. C1(atlas) hold skull; C2(axis) has a vertical peg (dens) to turn head.

Thoracic(mid-back/ T1-T12): Medium size; long sharp back bumps pointing down; smooth connection spots(facets) for ribs.

Lumbar (Lower back/L1-L5): Largest, thickest kidney-shaped bodies build to carry heavy weight; short square back bumps.

What are intervertebral disc and what are their 2 main parts?

What they are: shock absorbing cartilage cushions resting between vertebrae.

Part 1- Nucleus Pulposus (inner core): soft, gel-like center that flattens and bounces back to absorb shock when walking or jumping.

Part 2- Anulus fibrosus (outer ring): Tough ring of woven cartilage fibers wrapped around the gel core to hold it in place and bind bones together.

Memory tip: Nucleus=soft gel center; Anulus= Tough outer ring.

what are the 4 main jobs of the muscle system?

1. Movement: pulls on bones to move you and pushes food/fluids through internal Organs.

2. Posture: holds your body standing or sitting upright against gravity.

3. Joint stability: holds bone joints tightly together so they don’t slip out of place.

4. Heat Generation: produces heat whenever muscles contract to keep you warm.

how are muscles supplied with blood/nerves, wrapped in tissue, and arranged in fiber bundles?

Blood and Nerves (a/v/n): Every muscle gets 1 artery, 1 nerve, and 1 more veins.

Tissue Coverings (outer to inner):

Epimysium: wraps the whole entire muscle.

Perimysium: wraps a bundle of muscle fibers (fascicle).

Endomysium: wraps each single muscle fiber(cell).

Bundle (fascicle) shapes:

Circular: ring shape(lips/eyes)

convergent: fan shape narrowing to 1 point (chest)

Parallel: straight strap shape (thigh).

fusiform: thick middle, Tapered ends (biceps).

pennate: feather pattern.
memory tip: Epimysium (entire muscle)>Perimysium(package/bundle)> endomysium (each single fiber).

what is a neuromuscular junction and what are its 3 key parts?

what it is: the exact spot where a nerve ending meets a muscle cell membrane to send instructions to move.

3 key parts:

1. Branching Axon: the long nerve cable coming from. your spine.

2. Axon terminal: the swollen nerve tip that holds chemical signals.

3. Motor end plate: the folded pocket on the muscle cell membrane that receives the chemical signal.

what are the 4 functional roles muscles play during a movement?

4 roles:

1. Prime Mover(agonist): the main muscle doing the primary work for a movement.

2. Antagonist: the muscle that does the exact opposite movement.

3. synergist: a helper muscle assisting the prime mover.

4. Fixator: a helper muscle holding a bone completely still so the prime mover has a steady anchor.

what is the difference between direct and indirect muscle attachments?

Direct Attachment: outer muscle wrapping extends past the muscle as connective tissue:

Tendon: A strong, rope like cord connecting muscle to bone.

Aponeurosis: A flat, wide sheet of connective tissue connecting muscle to bone or other muscles.

what are the 7 rules used to make muscles?

7 rules:

1. Location: Nearby bone/region( temporalis= temple bone)

2. Shape: geometric shape (Deltoid=Triangle).

3. Relative Size: maximus (largest), Minimus (smallest), longus (long)

4. Direction of Fibers: rectus (straight vertical), transversus (sideways)

5. Number of origins: Biceps (2 heads), triceps (3 heads)

6. Location of attachments: connection points (sternocleidomastoid)

7. Action: movement done (flexor, extensor).

what do I need to know for muscle identification and actions?

study focus Use your 50 muscle flashcards!

For every muscle on Your List, master:

1. Visual spot: where it is located on a digram/ model

2. Exact name: correct spelling

3. Action: what movement it performs( flexes neck, closes jaw, extends arm)

How do extrinsic and intrinsic back muscles differ in development, nerve supply, and function?

Extrinsic Back Muscles:

Development:started outside the back in the embryo and migrated into the back.

Nerves: controlled by anterior rami of spinal nerves.

Function: move your arms or ribs.

Intrinsic back muscles (“true back muscles”):

Development:started directly in the back during development.

Nerves: controlled by posterior rami of spinal nerves.

Function: Hold posture upright and bend/twist spine.

What are abdominal aponeuroses and rectus sheath, and why are they important?

what they are:

Aponeuroses: flat tendinous sheets from side stomach muscles.

Rectus sheath: a protective sleeve made by these sheets wrapping around the front rectus abdominis (six-pack)

Why they are important:

1. keep internal abdominal organs safely tucked inside

2. join left and right sides of stomach together along the center line (linea alba)

3. protect blood vessels and nerves running along stomach wall.

How do skeletal, cardiac, and smooth muscle compare under a microscope?

Skeletal muscle:

control: voluntary (you control it)

Nuclei: Multiple nuclei along outer edges.

Cardiac Muscle (Heart):

Control: involuntary (automatic)

Look: striped(striated) ; branching cells joined by dark lines( intercalated discs)

Nuclei: 1 or 2 nuclei in center.

smooth muscle(organs):

Control: involuntary (automatic).

Look: No stripes(non-striated); pointed spindle-shaped cells.

Nuclei: 1 nucleus in center.