Skeletal System Flashcards
Functions of skeletal system
- Protects internal organs
- Stores and releases fat
- Produces blood cells
- Stores and releases minerals
- Facilitates movement
- Supports the body
Neurocranium
Protects brain
Made of series of flat bones
Pros and cons of neurocranium
Pressure can build up in there and cause damage
But it protects the brain
Medullary cavity
Stores fats
Yellow bone marrow
Bone marrow
Nutrients rich
Last resort of calories
Has progenitor stem cells
Yellow bone marrow can turn to red bone marrow if needed
Red bone marrow
Produces red blood cells
Hematopoiesis
production of all formed elements in blood stream
Happens in ends of long bones
Erythrocytes, Leukocytes, thrombocytes
Uses of calcium
-Action potential
-Muscle contractions
-Cell signal transduction
In what form is calcium stored in bones?
Calcium phosphate
Cells good at storing calcium in bones
Osteoblasts
Osteoclasts
Releasing calcium and phosphate into blood stream
Dense connective tissue
Outer layer of living bone
Periosteum
Thin layer of cells underneath dense connective tissue. Fibrous layer around outside of bone
Peri-
Round
-Osteum
Bone
Tendons
Connect muscles to bone
Ligaments
Connect bone to bone
Epiphysis
End of bone
Compact bone
On surface and ends of long bones. Bone is packed very close together
Spongy bone
Filled with bone marrow and trabeculae.
Types of bones
Long bones,
Flat bones,
Short bones and irregular bones
Short bones
Cube like
Where to find short bones
Carpals of wrist
Tarsals of ankle
Sesamoid bone
Round type of short bone
Patella
How many bones in adult skeleton?
206 on average
Irregular bones
No defined shape. Some surfaces flatter, some surfaces are more cuboidal.
Example of irregular bones
Vertebrae
Flat bone examples
Sternum
Rib
How many pairs of ribs
12
Basic anatomy of a long bone
- On proximal and distal ends of bone: articular cartilage
- Epiphysis: ends, has spongy bone
- Neck of bone: narrows down to shaft. Called metaphysis
- Diaphysis: mostly compact bone
Examples of long bones
Tibia
Fibula
Femur
Ulna
Radius
Humerus
Dia-
Across
Synovial joints
Help reduce friction between long bones.
Has synovial membranes that secrete synovial fluid
Appearance of synovial fluid
Looks like egg white
Viscous. Let’s epiphysis glide against eachother.
What kind of cartilage is articular cartilage?
Hyaline cartilage
Starts to wear out with age.
Avascular
Does not repair easily
Very vascular, supplied by nutrient artery,
Bone, can heal easily
How does bone grow when cartilage is worn ?
Get osteophytes.
Bone grows across joints. Causes pain.
Most people outlast their joints
Nutrient foramen
Openings in bones
Where blood vessels enter bones.
Sharpey’s fibers
Dense fibrous roots that connect periosteum to bone
Endosteum
Protective membranous layer inside of bone
Does not have fibrous layer
Has living layer of cells
Every carnivore
Break shaft to get bone marrow
Location of spongy bone
In middle of epiphysis
Location of medullary cavity
In middle of diaphysis
Epiphyseal line vs epiphyseal plate
Bone is done getting longer in epiphyseal line
Bone is still growing in epiphyseal plate. (Hyaline cartilage)
Fibrous layer of bone (periosteum is made of which tissue types?)
Dense irregular connective tissue
Components of bone
1.Calcium phosphate, mostly hydroxyapatite. Makes bones strong
2. Collagen:gives flexibility
Osteogenic cell
Progenitor stem cell that can turn into osteoblast
-blast
immature cell
Osteoblasts
Lay down calcium phosphate and collagen fibers as they create the Extracellular matrix. As they make bone.
Lacuna
Pocket where cell gets trapped
Lacuna latin meaning
Lake
Osteocyte
Completely trapped bone cell that maintains matrix
Channels that connect lacunae
Canaliculli
Cytoplasmic extensions of osteocytes move through
Canaliculli . Canals connecting lakes. Cytoplasmic extensions of cells connect and communicate to determine health of bone.
Component of bone matrix
Calcium phosphate, mostly hydroxyapatite
Collagen
Osteoclast
Multiple macrophages merge to break down bone. Put Calcium into blood stream
T/f osteoclasts and osteoblasts are always active?
True
Skeleton is continuously remodeled
Otic capsule
Bone around cochlea, Semicircular canals and vestibule
Never gets remodeled. Doesn’t get remodeled because it would affect hearing and static and dynamic equilibrium
Osteopenia
Beginning of porous bones.
Benefits of weight bearing exercise
Helps prevent osteoporosis by making bones denser and stronger
Flat bones anatomy
Compact bone on edges,
Spongy bone in middle where you find red bone marrow
Periosteum on both sides
Periosteal dura mater
Outer dense irregular connective tissue that protects brain and spinal cord in skull
On deep side of flat bone
Bone markings
Help understand function of a region of bone
Axial skeleton includes the
Auditory ossicles ,
Malleus, incus
And stapes in inner ear,
Skull, vertebral column
Rib cage
Hyoid bone
Hyoid bone
Only bone that doesn’t articulate with another bone. Sits on top of larynx
Appendicular
Everything that hangs a pin
Process
Sticks out often. Prominence or projection.
Ex:
On scapula has corocoid process, crow’s beak where pectoralis minor originates. Important insertion point for bones
Head
Top, very round
Example:
Head of femur
Fovea
Pit
Capitis
Head
Ligamentum teres
Connects head of femur into socket (Acetabulum)
Fossa
Deep groove.
Fossa example
Coronoid fossa on anterior humerus
Visceral cranium
Facial bones
Sinuses
Spaces in bone covered with mucous membranes that drain into nasal cavities. Increase surface area for mucous membranes
Act as resonance chambers
Lighten skull
Sinuses can cause pain when ?
They fill up with fluid which creates pressure
What happens to maxillary sinuses as you age?
They get larger, can go into roots of teeth
Types of bone markings
- Process,
- Fossa
- Fovea
- Tubercule
- Tuberosity
- Sinuses
Ischial tuberosities
Sitting bones
Resorbs bone
Osteoclasts
Anatomy of compact bone
Osteons
Unit of bone
Look like tree stumps
Lamella
Layers of osteons
Connected by collagen
Osteons are only found in
Compact bone. Gives strength
Trabeculae
Pointy parts in spongy bone .
Allows bone to be lighter.
Looks random but arranged along stress lines.
What makes spongy bone strong?
Remodeling, trabeculae laid down on stress lines
Structures in lamella that look like spiders
Lacunae, little pockets formed by osteoblasts
Dry bone vs living bone
Living bone has osteocytes. Legs from lacunae are canaliculli
What is in central canals
Artery, vein, nerve,
Lymphatic vessel
Perforating canals
Move blood, lymph and nerves from one central canal to another.
Bone is also highly innervates and lots of lymphatic vessels? T/f
True
Anatomy of spongy bone
Lacuna
Osteocytes
Osteoclasts
Canaliculli
Lamellae
Spongy bone lacks which structures
Perforating canals
Circular canals
Active red Bone marrow found in
Kids everywhere on spongy bone. Lots of hematopoiesis. As you get older hematopoiesis happens in epiphysis and long and flat bones, but less.
Bone marrow transplant materials are located in
Spongy bone in middle of sternum or from hip coxal bone
Bone remodeling
Caused by fractures. Osteoblasts and osteoclasts work together in a bone remodeling cone
How does bone remodeling work?
Bone remodeling cone, looks like a comet.
On head, has osteoclasts that break down bone and collagen,
on back has osteoprogenitor cells. Has reversal cells in transition zone from when we quit having osteoclasts and start having active osteoblasts .
Helps lay down bony matrix and collage
make bone
Angiogenesis
Occurs during bone remodeling. Helps lay down new arteries and new veins in middle of bone remodeling.
Occurs as central canal is created. Creates new nerves and new lymphatic vesicles
What can go wrong with bone remodeling?
Paget’s disease
problems in bone remodeling process, bone remodeling too fast, misshapen, less dense
which bone in lower leg doesn’t bear weight?
Fibula
Bone swaps
Can occur because bone is highly regenerative and highly vascularized
T/F : Fibula can replace parts of humerus
True
Where to find blood vessels in bone?
Epiphyseal plates, epiphyseal lines, medullary cavity,
Entering and exiting the bone through metaphysial artery and vein, nutrient foramen
Two types of bone formation
- Intramembranous ossification
2.
Intramembranous ossification
Formation of flat bones between mesenchymal cells
Mesenchymal cells
progenitor stem cells, through genetic control and molecular signaling we get the formation of osteoblasts or differentiation of cells, from progenitor stem cell into osteo blast
Osteoid
before matrix of calcium phosphate and collagen becomes organized. Not quite bone
In osteoid
Osteoblasts already trapped in lacunae, and become osteocytes, but have a fresh edge of osteoblasts on outer edges still laying down calcium phosphate and collagen.
Step 3 of membranous ossification
has trebeculae with blood vessels intertwined. Fibrous periosteum formed
Intramembranous ossification
ossification between two membranes is how flat bones are formed
Endochondral ossification
way long bones will form
Steps of endochondral ossification
- Mesenchymal cells differentiate into chondrocytes
- Cartilage model of the future bony skeleton and perichondrium form.
- Capillaries penetrate cartilage perichondrium turns into periosteum. Periosteal collar forms. Primary ossification center develops.
- Cartilage and chondrocytes continue to grow at the ends of bones.
- Secondary ossification centers develop.
- Cartilage remains at epiphyseal growth plate and at joint surface as articular cartilage
Primary ossification center
Forms at middle of bone
Diaphysis
Secondary ossification center
near the epiphyses
Explain endochondral ossification
Long bones lengthening
Hyperactive chondrocytes at epiphyseal plate. Divide rapidly and proliferate. Bone expands rapidly and down.
Calcification will happen and cartilage will get calcified. Osteoblasts and osteoclasts will come in and remodel the calcified cartilage into actual bone
Why do epiphyseal plates need lots of blood supply?
They are highly mitotically active
reserve zones contain
chondrocytes and a lot of hyaline cartilage matrix around chondrocytes
Proliferative zone
To make copies of. Makes copies of cells. Lots of mitosis and cytokinesis or cell division.
Maturing, hyperthrophy ,
rapid growth of chondrocytes and lipids
Where does the accumulation of chondrocytes, lipids, glycogen and alkaline phosphatase occur?
In the maturation and hypertrophy layer
Calcified matrix
cells start to die off. Right before zone of ossification.
How does bone lengthen?
Diaphysis under epiphyseal plates that lengthens on both ends
Open fracture
Sticks out through skin
Simple fracture
Does not break skin
Compound fracture
Breaks skin
Transverse fracture
Caused by forces on either side. Bone broken perpendicular to length.
Spiral fracture
Caused by twisting. Might look like a spiral.
Can be caused by trampolines often
Comminuted fracture
Little bits of bone in break. Bone fragments float around fracture line. Bone breaks into 3 or more fragments
Impacted fracture
Looks like zig zag, has jagged edges. Ends of bone jammed into eachother.
Greenstick fracture
Bone doesn’t break completely. Common in children
Oblique fracture
Bone breaks at angle
Stages in fracture repair
- Hematoma. Periosteum holds blood supply in place. Pocket of blood
- Formation of external and internal callus. Callus are undifferentiated tissues. Some unorganized calcified matrix. Some cells.
- Formation of bony callus. Callus becomes a bit more organized and has osteoblasts and osteoclasts come in. Osteoclasts get rid of rough edges and dead calcified cells. Osteoblasts lay down new bony matrix.
- Healed fracture. Little raised area of periosteum where fracture healed. Angiogenesis has taken place. New spongy bone has formed
Why is vitamin D important in bone Health?
Precursors made by liver and skin when exposed to sun. Fair skinned people absorb vitamin D very easily.
Relationship between kidneys and vitamin D
Kidneys activate vitamin D. When vitamin D is activated, that tells small intestines to absorb more calcium.
Kidneys can reabsorb more calcium when we need to do more bone growth
Which sex has more bone mass?
Men
At what age does bone mass start decreasing?
35-40
Most protective substance for bone mass
Estrogen
What happens to estrogen levels after menopause?
Women have very little estrogen after menopause. Men might produce more
Bisphosphonates
Slow down the activity of osteoclasts and bone remodeling cones.
Preserve bone density and mass
However with other issues might cause bone in maxilla or mandible to die
Theory of bisphosphonates
Slowed down osteoclasts and osteoblasts. Areas of bone that should’ve been remodeled more frequently weren’t.
Parts of skeleton where bone is older than it would normally be. Could cause osteonecrosis of jaw in some
Bone mass changes in space
Lose 1-2% of bone mass per month even with exercise.
Takes a long time to restore original bone mass
Amount of calcium needed in blood of young adult?
10 mg/ deciliter.
10 mg per 100 Mls of blood.
What happens when blood calcium levels get too high?
Action potentials in nervous system, muscle contraction, signal transduction
Thyroid gland function
Senses when calcium is too high.
Senses and releases calcitonin.
Causes osteoclast activity to be inhibited.
Less reabsorption of calcium in the kidneys
What happens is osteoclast activity is inhibited?
Osteoblast activity increases. More active osteoblast, fewer active osteoclast
What happens when calcium is too high?
- Thyroid gland releases calcitonin
- Osteoclast activity is inhibited
- Ca 2+ reabsorption in the kidneys decreases
- Ca2+ levels in blood decreases.
What happens when calcium is too low?
- Parathyroid glands release PTH
- Osteoclasts release Ca2+ from bone
- Calcium is reabsorbed from urine by the kidneys. Pull calcium from urine back into kidneys. But release phosphate
4.Calcium absorption in the small intestine increases via vitamin D synthesis. Kidneys will activate vitamin D
- Calcium 2+ level in blood increases
Osteogenesis imperfecta
Brittle bone disease
Mutation in genes that code for collagen.
Picking up infants can cause fractures.
Can cause blue whites of eyes. Blue coloring caused by misalignment in collagen of eyes.
-Genesis
Form
Fibrodysplasia Ossificans Progressiva
Rare
Formation of bone tissue that displaces normal tissue location
Continues over time.
Turns other tissues into bone over time.
Anchorage
Lets us walk, grasp objects and breathe
Ways cartilage can grow
Appositional and interstitial growth
Appositional growth
Bones grow in width
Happens on external face of existing cartilage tissue
Interstitial growth
Expands cartilage from within, lacunae bound chondrocytes secrete new matrix. Typically stops during adolescence.
Bony expansion carried on a narrow neck
Head
Round or oval opening through a bone
Foramen
Crest
Narrow ridge of bone
Tiny canals that connect the central canal of an osteon to the osteocytes
Canaliculli
Perforating canals
At right angles to central canal of an osteon. Connect the blood and nerve supply of the medullary cavity to the central canals.
What is not present in spongy bone?
Osteons
Tuberosity
Large rounded projection, may be roughened
Line
Narrow ridge of bone, less prominent than a crest
Tubercle
Small rounded projection or process
Epicondyle
Raised area on or above a condyle
Spine
Sharp slender often pointed projection
Process
Any bony prominence
Facet
Smooth, nearly flat articular (joint) surface
Condyle
Rounded articular projection. Often articulates with a corresponding fossa.
Groove
Furrow
Fissure
Narrow, slit like opening
Notch
Indentation at the edge of a structure
Meatus
Canal-like passageway
Sinus
Cavity within a bone, filled with air and lined with a mucous membrane
Fossa
Shallow basin-like depression in a bone, often serves as articular surface.
Trochanter
Large, blunt, irregularly shaped process
Medullary cavity contains which bone marrow in adults?
Yellow marrow
Site of most active red bone marrow in adults?
Hip bones
Where to find red bone marrow in adults?
Flat bones (More active)
Heads of femur
In spongy bone
Osteocytes maintain contact allowing them to communicate and permitting nutrients and waste to be related from one osteocyte to the next through
Canaliculli
Major organic fiber of the bone
Collagen
Endochondral ossification
Replacement of hyaline cartilage with bony tissue to form a bone
During infancy and childhood, the single most important stimulus of epiphyseal plate activity is _______from the anterior pituitary gland
Growth hormone
Describe long bones at the time of birth
A bony diaphysis with a widening medullary cavity and two cartilaginous epiphyses
Calcification zone
Surrounding cartilage matrix calcifies and chondrocytes die and deteriorate. Lets blood vessels invade. Leaves long, slender spicules of calcified cartilage at the epiphysis and diaphysis junctions which look like stalactites hanging from the roof of a cave.
Hypertrophic zone
Older chondrocytes in the stack, which are closer to the diaphysis hypertrophy or enlarge. Their lacunae erode and enlarge, leaving large interconnecting spaces
Proliferation zone
Cells at top epiphysis facing side of the stack next to the resting zone comprise the proliferation or growth zone. These cells divide quickly, pushing the epiphysis away from the diaphysis and lengthening the entire long bone.
Epiphyseal cartilage
Relatively inactive on the side of the epiphyseal plate facing the epiphysis. A region called the resting zone. Below the resting zone, the cartilage cells form tall columns, like coins in a stack that allow fast, efficient growth.
Calcification zone
Subsequently, the surrounding cartilage matrix calcifies and and these chondrocytes die and deteriorate, producing the calcification zone.
Thyroid hormone
Modulates the activity of growth hormone, ensuring proper bone formation.
In adolescence the growth spurt observed is attributed to an increase in
Sex hormones
Steps of intramembranous ossification
- Ossification centers develop in fibrous connective tissue membrane
- Osteoid is secreted and calcifies
- Immature spongy bone and periosteum form
- Compact bone replaces immature spongy bone, just deep to periosteum. Red narrow develops
What causes rickets
Vitamin D deficiency
What plays the major role in determining bone density?
Genetics
Excessive haphazard bone deposit and reabsorption
Paget’s disease
How to identify pagetic bone
Abnormally high ratio of spongy bone to compact bone. Reduced mineralization causes weakening of the bones.
Late in the disease
Osteoclast activity wanes, but osteoblasts continue to work, often forming irregular bone thickenings, or filling marrow cavity with pagetic bone.
Osteoporosis
Bone resorption outpaces bone deposit
Osteomalacia
Soft bones. Bones are poorly mineralized.
Rickets
In children. Bones are poorly mineralized. More severe than adult osteomalacia
Which bone disorder is not curable with increased calcium and vitamin D
Paget’s disease
Calcitonin
Lowers blood calcium levels when administered at high pharmacological doses
What happens during the formation of the fibrocartilage callus?
Activity of fibroblasts and osteoblasts creates an overgrown splint around the fracture site
How much of the skeleton is replaced every year?
5-10%
Function of parathyroid hormone
Promote activity of osteoclasts
Hormonal control of bone remodeling primarily involves which of the following?
Parathyroid hormone
Osteoblasts release
Matrix vesicles studded with the enzyme alkaline phosphatase
What can hypocalcemia do?
Cause hyperexcitability. Neuromuscular problems. Very sensitive to calcium.
Hypercalcemia can lead to
Non-responsiveness and inability to function.
Formation of kidney stones or deposits of salts in organs which affects their ability to function.
