Lecture - Bone Flashcards
What kind of coverings does a long bone have?
Periosteum (outside) and endosteum (medullary cavity)
Where is red blood marrow found?
- In children: in all bones
- In adults: converted to yellow bone marrow, but some remains in the axial skeleton (skull, vertebrae), and proximal heads of femur and humerus
What are the general features of the epiphyseal plate?
- hyaline cartilage
- separates epiphysis and diaphysis in children and adolescents
- growth zone in long bones
- cartilage expands to create bone length
- disappears when epiphysis and diaphysis join (around 18-20)
- epiphyseal line still visible in some adults
What are the 6 steps of endochondral ossification?
- Mesenchyme develops into a body of hyaline cartilage, covered with fibrous perichondrium
- Chondrocytes inflate and die in the primary ossification center in the middle of the cartilage, they calcify, then thin band of bone forms around the middle
- Vascular invasion, formation of primary marrow cavity, appearance of secondary ossification center
- Bone at birth: has enlarged primary marrow cavity and a secondary marrow cavity in one epiphysis
- Epiphyseal plate at distal end, ends filled with spongy bone, growth zone
- Adult bone: cartilage in the epiphyseal plate is consumed closing growth plate, primary and secondary marrow cavities merge into one
What does mineralization mean?
Mineralization is the processes involved in hardening of bone by deposition of calcium phosphate and other minerals; also called “calcification”
What does calcitonin do to osteoclasts and osteoblasts?
Osteoclasts are inhibited within 15 minutes
Osteoblasts are stimulated within an hour
What is the name for the study of bones?
Osteology
Where are osteogenic cells found?
The endosteum, inner surface of periosteum and in central canals
What does calcium do in the body?
muscle contraction and bone hardening
What causes hyperexcitability and tetany?
Hypocalcemia
What are the 4 types of bone (with example)?
- Long Bones - femur, humerus
- Short Bones - carpals, tarsals
- Flat Bones - sternum, cranium
- Irregular Bones - scapula, ethmoid
What are the 4 steps of fracture healing?
- Hematoma formation - blood clot
- Soft callus formation
- Hard callus formation
- Bone remodeling
What is the epiphysis?
The expanded head of a long bone
What are the 5 functions of the skeleton?
- Support
- Protection
- Movement
- Blood and immune formation
- Electrolyte balance - calcium, phosphorous and magnesium
Describe the organic portion of an osseous tissue
It makes up 1/3 of the dry weight of the bone
Composed of Collagen, Glycosaminoglycans, Proteoglycans, and Glycoproteins
What is a fracture where the skin is broken?
Open/compound
What is a fracture where the bone is in 3+ pieces or shattered?
Comminuted
What is responsible for phosphate and magnesium balance in the blood?
Osteocytes
Which hormone is secreted by the thyroid to lower blood calcium?
Calcitonin
What serves as the body’s storage for Calcium and Phosphorous?
The bones hold 99% of calcium and 90% of Phosphorous
What does the parathyroid gland release to raise blood calcium?
Parathyroid hormone (PTH) - moves calcium from bones to blood, stimulates osteocytes and osteoclasts to dissolve matrix (bone resorption)
How many bones are in the human body?
Around 206
What kind of bone cell has multiple nuclei (from many fused monocytes) and dissolves matrix by acids and enzymes?
Osteoclasts
Describe the general features of the endosteum
Reticular connective tissue that lines the medullary cavity
Describe the general features of perforating fibers
Collagen fibers of periosteum continuous with matrix
Which cells arise from trapped osteoblasts in the lacunae?
Osteocytes - they maintain (but do not make) the matrix (they synthesize the matrix) and manage blood calcium and bone calcium
How are signs and symptoms of leukemia related to a “space issue”?
It is cancer of the red bone marrow caused by out of control division of leukocytes, so there is less room for red blood cells and platelets
What is appositional bone growth?
Adding, matrix to the surface of the bone, occurs throughout life, widens bones, adds osteons to diaphysis of bone
Bone is twisted
Spiral fracture
Which kind of bone growth involves adding matrix to the interior of the bone, involves cartilage, and elongates bones?
Interstitial growth
What are the hormones of calcium homeostasis?
Calcitonin
Parathyroid hormone
Vitamin D
Calcitrol
What kind of fracture happens from abnormal trauma in a normal bone?
Stress fracture
Where is spongy bone found?
At the ends of longs bones and throughout other bones
What does an osteoclast release into the bloodstream?
Calcium from the bone
Describe yellow blood marrow
It is found in the shafts of long bones, arises from red blood marrow, can’t make blood cells, contains fat, in extreme situations it reverts to red blood marrow
Which cells makes collagen and glycosaminoglycans (GAGs) of the bone matrix?
Osteoblasts - they help mineralize and don’t divide, they cement themselves in to form bone
Describe a greenstick fracture
Bone is broken on one side, bent on the other, common in kids
What are the 4 major cell types found in bone tissue and what are their functions?
- Oteogenic/ osteoprogenitor cells - multiply continually
- Osteoblasts - bone-forming cells, activated by calcitonin
- Osteocytes - the ones in the lacunae
- Osteoclasts - break down bone, activated by PTH
In what kind of bone fracture do the ends remain in the anatomical alignment?
Nondisplaced fracture
Where in the spongy bone is red bone marrow found?
Withing the Trabeculae
Describe the developmental state of bones at birth
Cartilage is still present, especially in the skull
What hormone stops the kidney from excreting calcium, activates vitamin D synthesis, and increases phosphate excretion at kidneys?
PTH
What does Endochondral Ossification do?
Produce most of the bones in the body, starts with cartilage model then ossifies into a hard bone
What is a diaphysis?
Shaft of a long bone
Describe the general features of the periosteum
Dense irregular connective tissue with some collagen fibers continuous with tendons
What happens to cholecalciferol in the body?
it is hydroxylated by the liver into calcidiol (D2) and then the kidney into calcitrol (D3)
What is the cap of cartilage on the epiphysis of a long bone?
Articular cartilage
From what do osteogenic cells develop?
From mesenchyme (primordial soup, gel with stuff)
What does calcitriol do in the body?
Elevates blood calcium and phosphorous, bone deposition, increases intestinal absorption of Ca and P, reduces urinary excretion of Ca and P
What 7 tissues are found in a bone?
- Osseous tissue - osteon, osteocytes, canaliculi, lamellae
- Blood
- Bone Marrow - red and yellow
- Articular cartilage
- Adipose tissue - in yellow bone marrow
- Nervous tissue
- Other connective tissue - reticular
What is the purpose of the inorganic/organic composition of osseous tissue?
Resisting compression, tension, and bending
What is the most active form of vitamin D?
Calcitrol (D3)
What types of cells are produced in bone marrow?
Red blood cells
White blood cells
Platelets
List the 8 general features of long bone
- Epiphysis
- Diaphysis
- Metaphysis
- Medullary cavity
- Spongy (cancellous) bone
- Articular cartilage
- Nutrient foramina
- Coverings: Periosteum and endosteum
Where do minerals come from?
Diet
From what do osteoclasts arise?
Monocytes (a type of white blood cell)
What are the two primary steps of mineral deposition?
- Osteoblasts secrete collagen fibers
2. Calcium and phosphorous bind to the collagen fiber surfaces
What is hypercalcemia?
Too much calcium in the blood, causes depression of the nervous system, muscle weakness, emotional upset, cardiac arrest, ect.
Where does the trabeculae develop and why does it develop there?
Trabeculae develop along lines of stress to help your bones conform to your level and type of physical activity (how we know about activities of ancient societies)
What is the lattice of rods, plates, and spines found in spongy bone called?
Trabeculae
What is a pathological fracture?
Fracture in a bone weakened by disease
What is the significance of bones being living tissue?
Because they are living they are always changing even when they cease to grow
What is a closed fracture?
Fracture that doesn’t break the skin
Describe the process of mineral resorption
Bone calcium and phosphorous are dissolved into the blood by osteoclasts (influenced by hormones)
(think: braces - resorption on one side, deposition on the other to reshape teeth)
What is ossification?
Formation of bone
What is the name of the space inside a long bone that contains yellow marrow?
Medullary cavity
Which kind of bone growth can occur in adulthood and in which direction does it yield growth?
Appositional growth
What is the initial form of vitamin D released by the skin?
cholecalciferol
How does a bone calcify/mineralize?
The osteoblasts secrete a matrix (gel) and place minerals in it to harden it
How does Calcitonin lower blood calcium?
It moves calcium from the blood into the bones
Describe the inorganic portion of an osseous tissue and its composition
- Makes up 2/3 of dry weight of bone
- 85% hydroxyapatite (calcium phosphate)
- 10% calcium carbonate
- 5% Magnesium, Potassium, Sodium, and Fluorine
What is a metaphysis?
The narrow portion of a long bone between the epiphysis and the diaphysis
Which cells are capable of mitosis and are the source of new osteoblasts and osteocytes?
Osteogenic/ osteoprogenitor cells
What does magnesium do in the body?
Relaxes muscles
What kind of bones does Intramembranous Ossification produce?
Flat bones (ie in the skull) and most of the clavicle
What is the function of the ruffled border of an osteoclast?
Increasing secretion and absorption surface area
