Chapter 6 Cheat Sheet (DRAFT) by Amber.Farmer

Components of Skeletal System:

- Include all bones in the body
- Cartilage, joints, ligaments, connective tissue (stabilize or connect bone)

Functions:

1. Support - structural support for the entire body.
Soft tissue attachment and organs.
2. Storage - Yellow bone marrow stores lipids for energy reserves and mineral reserves for calcium and phosphorus ions held in calcium salts found in bone.
3. Blood Cell Production - red cells, white cells and other blood products are produced in the red bone marrow.
4. Protection - Protects tissues and soft organs by surrou­nding them with the skeleton. (ex. ribs protect heart/­lungs, skull protects brain)
5. Leverage - Bones function as levers to move the body with direct­ional force.

Features:

-The diaphysis is the central shaft that surrounds the marrow cavity (or medullary cavity) which is the center filled with bone marrow
- The epiphysis covered with articular cartilage. Articulate with an adjacent bone at a joint.
- Spongy Bone Network of bony rods or struts separated by space. Only located in the Epiphysis (The interlaced rods are known as trabec­ular). Red Bone marrow fills the holes between trabec­ulae. Red marrow is in this section.
- Compact Densely packed. Forms wall of the diaphysis, is composed of osteons.
-Marrow Cavity Soft fatty tissue. stores lipids and produces blood cell products. Yellow marrow and red marrow are located in the marrow cavity and Red marrow is found here.
Coverings:


- Outer surface is covered by periosteum
> Inner cellular layer
> Outer firbous layer - osolates bone from the surrou­nding tissue and forms attach­ments with fibers of tendons and ligaments

- Inner surfaces and spongy bone of marrow cavity covered by endosteum
> functions during bone growth and repair

- Embryonic develo­pment of bone:
> begins at week six of cartil­aginous formation and replaced with bone (process called ossifi­cation)

- Two types:
1. Intram­emb­ranous Ossifi­cation
2. Endoch­ondral Ossifi­cation

Calcif­ication occurs during ossifi­cation and can also occur in other tissues besides bone.

Osteog­enesis: (ossifi­cation - bone tissue formation)

Stages:
>Bone formation - begins in 2nd month of develo­pment
> Postnatal bone growth - until early adulthood
> Bone remodeling and repair - lifelong

Open vs. Closed Open projects through the skin. More risk of infection
Closed internal. Only seen in x-rays
Transverse break at right angle. Fracture of ulna- break a bone shaft across
its long axis
Displaced vs. non-di­splaced
Displa­ce-­produce new bone and abnormal bone arrang­ements-
snaps
in 2 or more places,
Non-di­splace- retain normal alignments of the bone fragments- breaks
all the way through, but does not move
Compre­ssion* vertebra under extreme pressure. Often caused by osteop­orosis
Spiral twisting stresses that spreads along the bone
Epiphyseal along the growth plate
Comminutedshattered the affected into a multitude of bony fragments
Greenstickonly 1 side of the shaft is broken. Normally happens in children

Movement- pull on tendons that move the bones.
Posture- continuous muscle contra­ction maintains body posture. Helps one sit up without falling over
Support – Abdominal wall and pelvic cavity floor composed of skeletal muscle. Support the weight of our visceral organs and shield our internal tissues from injury
Protection encircle opening of digestive and urinary tracts. Volunt­eering control over swallo­wing, defecating and urinating
Thermo­reg­ulation- muscles contra­ctions uses energy which generate heat

Connective tissues- Epimysium layer of collagen fiber that covers the entire muscle, separates the muscle from the surrou­nding tissues and organs. Perimysium divides the muscle into compar­tments aka fascicles. Contain bld vessel and nerve supply fascicles.Endomysium covers each muscle fibers and ties fibers together. Contains capill­aries and nerve fibers.
-Collagen fibers from all 3 layers come together to form
Tendon- bundle of fibers. Attaches muscle to bones
Aponeu­rosis Broad sheet of fibers. Connects muscles to each other.
Organ, fascicle, fibers
Fascicles or bundles of muscles fibers
Fibers each cell in the skeletal muscle tissue is a single fiber
A-band, I-band, H-band, Z-line, M-line
Z- marks the boundary at the end of each sarcomere (basic factional unit of muscle fiber-­array of thick and thin filaments) . Strands of protein connect the z lines to the thick filament to maintain alignment
M- located in the center of each sarcomere. Made of protein that connect central portions of the thick filaments
A- darker region running length of filaments. Includes zone of overlap containing both thin and thick filaments
I- light region containing the thin filaments. Includes the z line
H- when fibers is relaxed only contains thick filaments. Includes m line and light regions on either side
Thick vs. thin filament
Actin molecules are found in thin filaments. Extend inward towards the center of the sarcomere, they overlap thick
Myosis molecules are found in thick filaments

-Anaerobic ATP production(Does not require Oxygen)- Breaks glucose down to pyruvate. Occurs in the cytoplasm of the cell. Can still provide ATP when mitoch­ondria are limited by low oxygen levels. Yields 2 ATP per glucose. This is where you get lactic acid in your muscles.

_ Aerobic ATP Production(Needs Oxygen)- 95% of resting muscle cells use this type of ATP. This occurs in the Mitoch­ondria. Breaks down organic substrates through a series of chemical reactions. The end product of breaking down organic substances are ATP, water and carbon dioxide. (you get 15 ATP produced per pyruvate to enter the citric acid cycle.)

1. Nervous System Signal:
> Sends an action potential down an axon of a neuron (nerve cell).
> At axons end or terminal switch to a chemical messenger.
> Acetyl­choline Release ---> crosses synaptic cleft.


2. Muscle Release Calcium:

> motor end fo the muscle cell has received the acetyl­choline signal.
> Muscle cell sends an action potential down muscle cell.
> This shock releases calcium from the sacrop­lasmic reticulum (sarco­lemma, t tubules, transverse tubules)

**3. Contra­ction (Sliding Filament Theory):

> Calcium Binds troponin
>Tr­oponin changes shape and moves tropom­yosine out of the way to open the actin myosine (active) binding sites
> myosine heads do a powers­troke mostion by grabbing onto the exposed actin sites and pulling.

4. Relase:

>ATP gets hydrolized into a ADP + P
> the hydrol­ization releases energy
> calcium is stored back into the sacrop­lasmic reticulum
> Acetyl­choline is broken down with acetyl­cho­lin­estrase (if this is turned off you become paraly­zed).

-Isotonic Contra­ction- Tension rises and the skeletal muscle's length changes. Tension remains constant until relaxing Example Push-ups. Moveme­nt/­sho­rtening of the muscle.

-Isometric- Muscle Length stats the same. Tension produced does not exceed the load. There is no movement required. Example holding yourself in a plank or pushing against a wall.

-Incomplete Tetanus Producing almost peak tension during rapid cycles of contra­ction and relaxa­tion. Example Charlie horse.

-Summation- Addition of one muscle twitch to another. Causes a more powerful contra­ction. Causes a second stimulus to arrive before the relaxation phase has ended. Example working out.

-Complete Tetanus- Occurs when rate of stimul­ation increased until relaxation phase is elimin­ated. Produces maximum tension and continuous contra­ction. Results in high calcium ion concen­tration in the cytosol. Example Fight or Flight response adrenaline rush.

-Small Motor unit- sustained muscular contra­ction. Lower threshold for activa­tion. Example upright posture

-Large Motor unit- Generate more force, but have sparce mitoch­ondria there for easily fatigued. Example Jumping.

Charac­ter­istics:

-Supports connective tissue containing cells in a matrix
-Cells are called osteocytes
- The matrix contains: Calcium Salts in the form of calcium phosphate (which makes up 2/3 the weight of bone) & Extrac­ellular Protein Fibers (about 1/3 the weight of the bone).

Bone Catego­ries:

1. Long Bone - Longer than they are wide (ex. femur and humerus)
2. Short Bone - wide as they are short (ex. wrist and ankle)
3. Flat Bones - Thin, broad, and light (ex. parietal bones in skull, ribs and shoulder blades)
4. Irregular Bones - Don't fit in any other category (ex. vertebrae, sacrum)

Bone Charac­ter­istics
5. Compact Bones - Densely packed (ex. form the diaphysis)
6. Spongy Bone - Projection of bones separated by space (ex. on all bones)

Membrane bone develops from fibrous membrane (forms flat bone like clavicles, cranial bones, and mandible)


-Occurs during fetal develo­pment where bone develops within sheets of connective tissue.
- Starts in a ossifi­cation center
- Osteob­lasts differ­entiate from connective tissue stem cells and form new calcified bone matrix.
- Bone matrix formation extends outward
- Osteob­lasts surrounded by the matrix change into osteocytes
- Blood vessels grow into area and are trapped within the developing bone.
- Bone remodeling produces osteons of compact bone


>Re­sults are flat bones like the cranial bone and clavicles.

Bone resorption and deposit- Osteoclast is the erode the bone from the inside that gets absorbed by the body. Osteoblast is deposit from the outer bone-i­njury
Osteoc­lasts and Osteoblast- clast most abundant cell in body. Maintain bone structure by recycling calcium salts. Contin­ually remove matrix. BLAST- contin­ually build matrix
Vitamin D- Released by the skin. Increases blood calcium levels. It allows the intestines to absorb calcium. Without Vitamin D we can not absorb calcium
Calcitrol- Released by the kidneys. increases calcium levels in the blood. Stimulates osteoc­lasts. (Hollowing out the bone)
Parath­yroid Hormone- Parath­yroid Increased blood calcium. Stimulate Osteoc­lasts.
Calcitonin-released by the thyroid. Lowers calcium levels in the body fluids. Released by osteob­lasts. (Bricks building a wall.)

-Osteopenia- Bones become thinner and more weaker as a normal part of aging. (Everyone becomes slightly ostepenic as we age). People start to lose the mass of their bones between the ages of 30 and 40. Once it begins women lose roughly 8% of their bone mass while men lose about 3% per decade. "Not all parts of the skeleton are equally affect­ed"

-Osteop­orosis- That reduces bone mass so much that normal function is compro­mised. The difference between the normal oseopenia of aging and osteop­orosis is a matter of degree "Sex Hormon­es". Over the age of 45, an estimated 29% of women and 18% of men have osteop­orosis. Women get it early because of menopause. Men get it at a much later age because they still produce sex hormones

-Osteom­alacia- Softening of bones dues to demine­ral­iztion. (low levels of calcium, phosphate or vitamin D. Could also be increase in calcium resorption out of bone.) This would just be a Calcium defici­ency.

-Arthritis- Damage to synovial lining of joints. It causes grinding and further damage during articu­lation. Cortisone shots can decrease the inflam­mation.

-Rheumatoid Arthritis- It is an auto-i­mmune disorder. This is where your immune system improperly attacks the body's own tissue. It is treatable with immuno­sup­pre­ssants, in addition to cortli­cos­ter­iods.

-Rickets- Disease where lack of calciu­m,p­hos­phate or vitamin D prevents proper bone develo­pment, leaving bones weak and deformed. Usually in children.

-Synart­hrosis- Immovable joints. Joints are fused together. "­Syn­-" Together, "­Art­hr-­" Joint, "­-os­is" Condition.
Classi­fic­ation of Synart­hrosis joints
Suture- Connects skull bones with dense connective tissue
Gomphosis- A Ligament binding each tooth in the socket.
Syncho­ndrosis- A hyaline carila­ginous connection between the first pair of ribs anad the sternum (all other rib-st­ernum joins are synovial)

-Amphia­rth­roses- Limited Movement. condition where a joint is a both movable and immovable. (A joint that is slightly movable) "­Amp­hi-­" both, "­Art­hr-­" Joint, "­-os­is" Condition.
Classi­fic­ation of Amphia­rth­roses joints
Syndes­mosis- Fibrous joint connected by a ligament, attaches tibia to fibula and radius to ulna.
Symphysis- bones separated by fibroc­art­ilage pad, between the pubic areas of coxal bones as well as interv­ert­ebral discs.

-Diarth­roses (Synovial Joints)- Freely movable joints. Joints can move two ways (back and forth). These are movable joints. Most common joints. Covered in Synovial Fluid.

-Flexion- The movement in the anteri­or-­pos­terior or sagittal. plane that decreases the angle between articu­lating bones.

-Extension- Occurs in the same plane as flexion, but it increeases the angle between articu­lating bones.

-Abduction-Movement away from the from the body in the frontal plane. Example swinging the upper lib to the side is abduction of the limb.

-Adduction- Moving the swinging body part back to the anatomical position. Example Throwing a ball and bringing your arm back to your side.

-Circum­duction- Moving your limb in a 360 degree circle. Example drawing a circle with your leg or arm.

- Rotation- involes turing around the longit­udinal axis of the body or limb. Example turning your head left and right.

-Pronation- Moving your palm from facing the front to facing the back.

-Supination- Moves palm from facing the back to facing the front.
Example you use pronation and supination when you turn a doorknob.

-Inversion- Twisting motion of the foot that turns the sole inward, elevating the medial edge of the sole.

-Eversion- Twisting motion of the foot that turn the sole outward, lowering the medial edge of the sole.

-Plantar flexion- Extension at the ankle. Example Pointing the foot downward.

-Dorsif­elxion- flexing of the foot. Example point the toes up to your face.

Osteons:
- Unit that makes up compact bone (Haversian System)
- Lamillae (Haversian Canal) hollow tubes of the bone matrix ,which are calcified, are placed outside but next to each other to form rings similar to those of a trees growth rings.
- Lacuna are holes between the lamillae
- Osteocytes(bone cells) are the red blood cells located in the lacuna
- Perfor­ating Canals are the pathways for blood to be linked to other vessels in the periosteum and marrow cavity.
- Canalculi are hair like fiber channels connecting lacuna to each other and the central canal blood vessels for nutrie­nt/­waste exhange. The contain cytopl­asmic extensions of the osteocytes and radiate through the matrix.
- Trabeculae are rods formed by the lamellae that create the support network of bones.

Three major types of joints:

Fibrous:
> usually connected by dense connective tissue and this connective tissue is rich in collagen fibers.
> immovable and typically interlocks with irregular edges.
> divided into three subcat­egories called suture, syndes­moses and gomphosis.
- Suture - Fibrous connection plus interl­ocked surfaces. (Between the bones of the skull)
-Synchr­ond­rosis - Inter postion of cartilage bridge or place (between first of ribs and the sternum).
-Gomphosis- found at the articu­lation between the sockets of the maxilla and the teeth. This fibrous tissue connects the socket and tooth with the period­ontal ligament.

Cartil­age­nous:
> connected fibroc­art­ilage or hyaline cartilage. This type of fibrous joint allows more movement but still less than the synovial joint.
- Primary - example of the primary or syncho­ndroses joint is a epiphysial growth platers.
- Secondary - an example of the secondary or symphyses is interv­ert­ebral discs and pubic symphysis.


Synovial:
> the most common of joints and allows the most movement
> This type has a synovial cavity and is connected by dense irregular connective tissue that forms an articular capsule surrou­nding the bones articu­lating surfaces.
> connects bones with a fibrous joints capsule that is continuous with the perios­teum. The joint capsule consti­tutes the boundary of the synovial cavity and surrounds the bones articu­lating surface. These cavities are filled with synovial fluid and examples of these are knees or elbows.

There are many factors that affect joints stability; those factors are if the bones of the joints interlock, how deep the joint sits, if there are ligaments or smaller bones supporting that joint, and the amount of mobility available in the joint.
An example of the mobility factor: The shoulder has a wide range of mobility and is more likely to be dislocated then other joints.
An example of ligaments and smaller bones supporting factor: The kneecap
An example of how deep a joint sits factor: The hip
An example of interl­ocking bones factor: The elbow

Role Calcium:
- contra­ctions starts with the arrival of calcium ions within the zone of overlap, they then bind to troponin.

Troponin:
- when calcium binds to troponin to weakening the bond between actin and the tropon­in-­tro­pom­yosine complex.


Tropom­yosine:
-Tropo­myosine is moved out of the way exposing the actin sites.


Actin:
- Actin is exposed during the weakening of the bond between troponin and tropom­yosine. Then myosine heads are able to grab onto the exposed actin forming a cross bridge.


Myosine:
- Myosine heads are able to grab onto the actin sites (this is called a cross bridge because stored energy is pulling the myosine head toward the m line) and pull along them to conract the muscles. This is called a powers­troke motion and as a result the bound ADP and phosphate groups are released.


ATP:
- when another ATP binds to the myosine head the link between myosine and the active site on the actin molecule is broken. This exposes the active site allowing the next myosine head to form another cross bridge.

Myosine Reacti­vation:
- occurs when the free myosine head splits the ATP into ADP + P. The energy released is used to recock the myosine head.