​Review Question:
what is the purpose of a bone marrow transplant?

Glucocorticoids...

= ​stress

​Review Question:
explain how the RANKL system
plays a role in bone remodeling.

vitamin C and K also stimulate osteoblast differentiation

 Bone marrow
 is the tissue found in the medullary cavities and spongy bone of long bones.
There's red bone marrow (myeloid tissue) and yellow bone marrow (fatty tissue). 
Red marrow houses stem cells which are able to differentiate into WBCs used to fight infections, RBCs which carry O2 and platelets which participate in clot formation. 
Yellow marrow is stored fatty tissue but also contains stem cells which give rise to fat, cartilage, and bone.

​Review Question:
describe four determinants of bone mass.

Finding a match for a bone marrow transplant involves identifying a donor with compatible Human Leukocyte Antigens (HLAs), which are proteins found on the surface of white blood cells. The ideal match has the same HLA markers as the recipient.

 Osteoclasts 
​release enzymes that release calcium from bone, decalcifying the matrix.

          bone remodeling

 osteoporosis

OPG acts as a decoy receptor that inhibits RANKL's signaling. The balance between RANKL and OPG affects bone mass.

Excessive production of GH in children (before the epiphyseal plates fuse) results in  gigantism and continued growth of long bones.

RANKL stands for
​ 'Receptor Activator of NF-κB Ligand'.
It is a cytokine (cell messenger) crucial for bone resorption. It acts as a ligand, binding to its receptor RANK on
stem cells. This triggers them to  differentiate into osteoclasts
leading to bone resorption.

​   how long bones
            lengthen

 Calcitonin acts to reduce blood Ca+ levels.
Calcitonin inhibits the activity of osteoclasts and decreases the resorption of calcium by the kidneys. 
Parathyroid hormone (PTH) acts to resorb calcium from the bone and increase calcium resorption by the kidneys increasing
blood Ca+ levels.

​Review Question:
what is bone marrow?

​how are the two types of marrow  different?

          Our Skeletal System

​the softening  of bones in children. Rickets occurs often because of extreme
vitamin D deficiency.

 Hormonal control of bone remodeling:
Calcitonin and Parathyroid Hormone (PTH)

 The synthesis and degradation of bone is controlled by the RANKL system. RANKL is released by osteoblasts. RANKL binds to RANK receptors on the surface of stem cells and triggers them to differentiate into osteoclasts.

This is a another example of a ligand/receptor system.

PTH stimulates the secretion of RANKL

 pathology

GH imbalance

Rickets is a condition that causes a child’s bones to soften and weaken. This makes them bend and warp, often leading to bowed legs. It also causes bone pain and makes them break more easily. The most common cause of rickets is a vitamin D deficiency. This occurs when a child doesn’t get enough vitamin D from the foods they eat or exposure to the UV radiation from the the sun.

 Review Question:
explain the hormonal control of the bone remodeling process.

​​ Osteoblasts secrete a new matrix of collagen and calcium salts. 

 Calcitonin and PTH are antagonists

When the area around the osteoblast calcifies into this matrix, the osteoblast becomes trapped in this bony matrix within a space called the lacuna and transforms into an osteocyte. 

    compact bone structure

​ Just an FYI re actual complexity of process...yikes! 

Thyroid hormone T3/T4 balance is important for bone integrity

Hyperparathyroidism

​overactivation of osteoclasts due to  parathyroid tumors stimulating the over secretion of PTH leading to
very high blood Ca+ levels

OPG is stimulated by estrogen.
​OPG blocks RANKL from binding to RANK so decreases osteoclast activity.
low estrogen levels leads to increased osteoclast activity and weaker bones. 

Bone marrow transplants are used to treat conditions where the bone marrow isn't functioning properly, such as leukemia, aplastic anemia, and sickle cell anemia. They can also be used to restore bone marrow function after high-dose chemotherapy or radiation therapy.  

​   how long bones
            thicken

 The human body has 206 bones   
        There are 26 bones in the foot
​               The hand and wrist contains 54 bones
                        The femur is the longest and strongest bone
                             The stapes, in the middle ear, is the smallest and lightest bone
                                 Only the hyoid bone isn't connected to another bone
                                    Only 10% of the world's animals have an internal skeletal system

Rickets 

the bone remodeling process

​Review Question:
explain how long bones thicken

bone mass determinants