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A&P Ch.5: Skeletal System


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What terms refer to bones?
-os and -oster
What are the primary functions of the skeletal system?
-structural support
-storage of minerals and lipids (Ca, P, lipids in yellow marrow)
-blood cell production
-leverage: change the magnitude and direction of forces generated by skeletal muscles.
What are the two types of bones?
-cancellous bone (sponge)
Describe compact bone
-very heavy and dense
-makes up shafts of long bones and outside layer of ALL bones
-consists of many tiny, tightly compacted, laminated tubes known as the haversian system.
Describe Sponge bone
-looks like a sponge
-cinsists of tiny "spicules" of bone that appear randomly arranged with lots of spaces between them (light but strong)
-helps lighten bones without reducing strength
-found in extremitites of long bones and between two layers of compact bones (dipole) as in the skull.
What are the 4 bone shapes?
1) long bones
2) short bones
3) flat bones
4) irregular bones
What are the segments of long bones?
What is the diaphysis?
A long tubular shaft made of a marrow cavity and a compact bone wall.
What is the epiphysis?
The ends of long bones which consist largely of spongy bone with a thin covering of compact bone
What is the metaphysis?
A thin zone where the diaphysis begins tapering outward.
Where are long bones mostly found?
In the extremities such as the humerus, radius, ulna, metacarpals, phalanges, pelvic limb, femur, etc.
What are short bones?
boxy or approximately equal in all dimensions. They consist of a core of sponge bone covered by a thin layer of compact bone. NO marrow cavity but some marrow!
What are short bone function?
Absorbing concussion. Found in complex joints: carpus and tarsus.
What are flat bones?
thin, roughly parallel surfaces that resemble a spongy bone sandwich.
What do flat bones function as?
Protection of vital organs and procide large areas for attachment of muscles. Ex; skull, pelvis, scapulas.
What are irregular bones?
Bones that don't fit in a specific category. They are complexely shaped with short, flat, notched, and rigid surfaces.
Where are irregular bones often found?
Unpaired and along medial plane. Ex; vertebra and some skull bones.
What is the largest sesamoid bone in the body?
The patella.
Describe Osseous tissue
-Dense, supportive connective tissue
-Contains specialized cells
-Produces solid matrix of calcium salt deposits
-around collagen fibers
What is the periosteum?
It covers the outer surfaces of bones and cinsists of an outer fibrous and inner cellular layers
What makes up the matrix of bone?
-Calcium phosphate
-Collagen fibers
-Protein (collagen) and crystals (CaP)
What are the bone cells?
How much mass to they make up?
-osteoprogenitor cells
-they make up 2% of mass
What are osteocytes?
How do they connect with one another?
Non-dividing, mature bone cells that maintain the bone matrix and live in lacunae. They are found between layers of matrix (lamellae).
-Connect through cytoplasmic extensions through canaliculi in lamellae.
What are osteoblasts?
These produce new bone matrix by synthesizing and secreting an organic matrix (osteoid).
What are osteoblasts surrounded by bone called?
What are osteoprogenitor cells?
they are mesenchymal stem cells that divide to prduce osteoblasts. They are located in inner, cellular layer of periosteum to assist in facture repair (located where needed and will become osteablasts).
What are osteoclasts?
They are giant multinucleated cells that are derived from stem cells that produce macrophages and secrete acids and protein-digesting enzymes to dissolve bone matrix releasing stored minerals.
What is homeostasis in bones?
Bone building and bone recycling must balance or weakness occurs. Exercise maintiains bone building.
What is the basic funtional unit of the compact bone?
osteon or the Haversian system.
What is the osteon?
the basic unit of mature compact bone where osteocytes are arranged in concentric lamellae. This is around a central canal containing blood vessels.
What are perforating canals?
Perpendicular to the central canal that carry blood vessels into bone and marrow.
What are circumferential lamellae?
Lamellae wrapped around the long bone and binds osteons together
How does spongy bone compare to compact bone in terms of osteons?
They don't have any. The matrix forms an open network of trabeculae which have no blood vessels.
*Spongy bone is covered in compact bone however.
What is bone marrow?
A specialized type of soft, diffuse connective tissue (myeloid tissue) where blood cells are produced. It can be found in long bones and spaces of spongy bone.
What is red marrow?
forms blood cells, found in virtually all bones in young animals
What is yellow marrow?
Marrow cells have become saturated with fat and are inactive. Yellow can go back to red during times of decreased blood supply.
What is the endosteum?
Lines the marrow cavity and the inner surfaces of central canals, covers the trabeculae of sponge bone.
When do human bones stop growing?
Around 25 years of age.
What is osteogenesis?
Bone formation
What is ossification?
the process of replacing other tissues with bone
What are the two ways bone can form?
1) Endochondral formation
2) Intramembranous formation
What is intramembranous formation?
Bone develops directly from mesenchyme or fibrous connective tissue. Normally occuring in deeper layers of dermis (AKA dermal ossification)
What is endochondral ossification?
Bone replaces exsisting cartilage. Most common formation this way.
What is interstitial growth?
It is the epiphyseal plate that allows the diaphysis of a long bone to increase in length.
What is appositional growth?
1) bone formation makes parallel ridges to blood vessel.
2) Ridges enlarge to deep pocket
3) Ridges meet and fuse trapping the vessel inside
4-6) bone continues entrapping vessels and increasing in diameter.
What are three vessel sources of blood supply?
-Periosteal vessels
-Nurtrient artery and vein
-Metaphyseal vessels
How do periosteal vessels work?
Countless tiny vessels from the periosteum penetrate into bone matrix through perforating caals and interconnect osteons.
How does the nutrient arter and vein work?
Supplies large bones by carrying blood in and out of bone marrow.
How do metaphyseal vessels work?
They supply blood to inner surfaces of each epiphyseal cartilage.
How does exercise help maintain bones?
Stress applied to bones are essential to maintain bone strength and mass. Over a few weeks of inactivity, 1/3 bone mass can be lost!
What do animals need for normal bone growth?
-nutritional and hormonal factors
What are the needed minerals for proper maintenance of bones?
-Ca and P salts
-small amounts of Mg, F, I, and Manganese.
What vitamins are needed for bone maintentance and what are they applied for?
-Vit C for collagen synthesis and stimulating osteoblast differentiation
-Vit A to stimulate osteoblast activity
-Vit K and B12 to help synthesize bone proteins
What are some hormones needed for bone growth?
-Growth hormone
-Sex hormones
-Parathyroid hormone
What three participants help with hormone control and how?
Bones store calcium ions
Digestive tract absorbs calcium ions
Kidneys excrete calcium ions
What are the two hormones with opposite effects that help with homeostasis through neg. feedback?
Calcitonin and Parathyroid hormone (PTH).
What happens when blood calcium gets too high?
Calcitonin is released. This makes the kidneys allow for calcium loss, rate of intestinal absorption decreases, and osteoclasts are ininhibited while osteoblasts put calcium ions into bones (and therefore out of blood).
What happens when blood calcium gets too low?
Parathyroid Hormone kicks in. Osteoclasts stimulated to release calcium ions, kidneys retain calcium ions, and rate of intestinal absorption increases.
What are the skeletal systems in animals (2-3 depending on animal)
1) axial
2) appendicular
3) visceral
What are articulation?
Joints: junctions between bones. arthro- and articular refer to joints
How can you classify joints (articulations)?
What are the functional classes of joints?
What are the structural classes of joints?
Bony fusion
Fibrous joint
Carilagenous joint
synovial joint
What are synarthroses joints?
What are the subdivisions of synarthroses joints?
-immovable joints
What is a suture joint?
A fibrous synathroses joint. Only located between the bones of the skull. The edges of the bones are interlocked and bound together at the suture by dense connective tissue.
What is a gomphoses joint?
A fibrous synarthroses joint that binds teeth to bony sockets in the jaw.
What is a synchondroses joint?
A cartilaginous synarthrosis joint that is a rigid cartilaginous bridge between two articulating bones such as the epiphyseal plate.
What is a synostoses joint?
A bony fusion synarthrosis joint that is created when two separated bones fuse and the boundary between them disappears, such as epithyseal lines of mature bones.
What are amphiarthrosis joints?
What are the subdivisions of amphiarthrosis joints?
-Slightly moveable joints.
What is a syndesmosis joint?
A fibrous amphiarthrosis joint where bones are connected by a ligament, such athe distal joint between the tibia and fibula.
What are the functional classes of joint?
What are sutures?
fibrous synarthrosis joints where the edges of bones are interlocked and boun together at the sutrure by dense connective tissue. Only located between skull bones.
What are gomphoses?
Fibrous synarthrosis joint bolting together of teeth to bony sockets in jaw bones.
What are synchondroses joints?
Cartilaginous synathrosis joints that are a rigid, cartilaginous bridge between two articulating bones such as the epiphyseal plate.
What are synarthroses joints?
Immovable joints:
What are amphiarthroses joints? Subclasses?
Slightly moveable joints that include syndesmosis and symphysis joints.
What is a symphysis joint?
A cartilaginous amphiarthrosis joint where the articulating bones are separated by a wedge or pad of fibrocartilage, such as the joint between the bodies of vertebrae.
What are diarthrosis joints?
Freely moveable joints. Also known as synovial joints.
Describe the articular surface of the synovial joint?
It is a smooth, thin layer of compact bone over the top of cancellous bone
Describe the articular cartilage of synovial joints.
It is hyaline cartilage that lies on top of the articular surfaces. Functions like a teflon coating to reduce friction.
What is the joint cavity filled with and what for?
Synovial fluid for lubricating, absorption, and nutrient distribution.
What is the articular capsule in a synovial joint? What are its parts?
The multilayered joint capsule surrounding the joint cavity.
-outer layer: fibrous tissue
-lining layer: synovial membrane which prduces the synovial fluid.
What are some accessory structures in synovial joints?
fat pads
What are stabilizing factors in synovial joints? Such as?
They prevent injury by limiting the range of motion:
-collagen fibers
-articulating surfaces and menisci
-other bones, muscles, or fat pads
-tendons of articulating bones
What are some types of dynamic motion?
linear (gliding)
angular (circumduction)
What are the planes fo dynamic motion?
Describe linear motion.
2 surfaces slide past eachother, such as the movements between the carpal and tarsal bones.
Describe flexion and extension:
Movement in the sagittal plane that reduces the angle or increases the angle between the articular elements
Describe abduction and adduction:
Abduction moves a part away from the median plane of the body.
Adduction moves a part toward the median plane.
What is circumduction?
Moves a part so it's distal end moves in a circle
What is rotation? What types are there?
-Pivoting a bone on its axis
-lateral or external or outward
-supination (hand palm up)
-pronation (hand palm down)
How are joints classified by shape?
What is a gliding joint?
Flattened or slightly curved faces with limited motion.
What is a hinge joint?
An angular motion in a single plane (monaxial)
What are pivot joints?
Rotation only (monaxial)
What are ellipsoidal joints?
Oval articular face within a depression with motion in two planes (biaxial)
What are saddle joints?
2 concave faces, straddled (biaxial)
What are ball-and-socket joints?
Round articular face in a depression (triaxial)

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