Cellular Biology Flashcards
What is the structure of trabecular bone?
→ spongy → interlocking struts with spaces inbetween
What are osteocytes?
→ Terminally differentiated osteoblasts
What is the RANK ligand produced by and what does it do?
→ Produced by pre-osteoblasts, osteoblasts and osteocytes → binds to RANK and stimulates osteoclast differentiation
State the 7 organisation levels in the body
- Organism level
- Systems level
- Organ level
- Tissue level
- Cellular level
- Organelle level
- Chemical level
What are the two subtypes of bone marrow cells?
→ Mesenchymal cells → Haematopoietic cells
What does the RANK receptor binding promote?
→ osteoclast differentiation
What is a common bone disease?
→ Osteoporosis
What is ground substance?
Substance in the extracellular space that contains all components of the extracellular matrix (ECM)
Mainly water and hygroscopic proteoglycans
What happens after the Wnt pathway is activated?
→ beta catenin is translocated to the nucleus where it causes transcription
What is the structure of trabecular bone?
→ spongy → interlocking struts with spaces inbetween
What are the three main components of connective tissue
- Ground substance or matrix
- Cells
- Fibres (elastin and collagen)
What happens after the Wnt pathway is activated?
→ beta catenin is translocated to the nucleus where it causes transcription
What do haematopoietic stem cells give rise to?
→ Lymphoid lineage - lymphocytes → Myeloid lineage - RBC and macrophages
How is cortical bone organised?
→ In sheet like structures → Surrounding a hollow structure called the Haversian canal
What are the 4 main types of connective tissue
- Connective tissue proper
- Cartilage
- Bone
- Blood
What do OPG and NO do?
→ Inhibit the differentiation of osteoclasts
What 2 changes occur during osteoporosis?
→ Thinning of the cortical bone → Widening of the trabecular bone
What are the functions of connective tissue
- Binding of organs
- Support
- Physical protection
- Immune protection
- Movement
- Storage
- Heat production
- Transport
How is bone continually renewed?
→ Old bone is continually resorbed and new bone is laid down → Cycle between osteoclasts digesting old bone and osteoblasts laying down new bone
What is the life cycle of osteoclasts controlled by?
→ Apoptosis
Where are osteocytes found?
→ Encased within the bone matrix
What is delayed skeletal growth in men linked to?
→ Aromatase deficiency
An individual skeletal muscle cell
Muscle Fiber
What are the 5 functions of bone?
→ Support and movement → Protection for internal organs → Bone marrow store → Mineral reservoir → Endocrine
What do PGE2, NO and ATP promote?
→ Differentiation of osteoblasts
Describe simple squamous epithelium
What is the function of trabecular bone?
→ Makes bone lighter
What does the RANK ligand promote?
→ Promotes the differentiation of osteoclasts
Where is cortical compact bone found?
→ On the outside
What are the 5 functions of bone?
→ Support and movement → Protection for internal organs → Bone marrow store → Mineral reservoir → Endocrine
What are the 3 factors that control bone remodelling?
→ Load bearing exercise → Cytokines and local signals → Endocrine
What are the 2 functions of osteoclasts?
→ Bone reabsorbing - digest old bone → Dissolve bone mineral and have enzymes to digest the organic matrix
Where is cortical compact bone found?
→ On the outside
What is a protease that osteoclasts secrete?
→ Cathepsin K
Describe stratified epithelia
- Two or more cell layers (20 or more)
- Regenerate from below
- Basal cells divide, cells migrate to surface
- Mechanism of epidermis replacement
- More durable than simple epithelia
- Physical protection is major role
What are lacunae?
→ cell sized holes within the bone matrix
What is sclerosteosis caused by?
→ Mutation of the SOST gene → Inactivating sclerostin protein
What is OPG?
→ A soluble protein produced by osteocytes
What does OPG do?
→ Acts as an antagonist → binds to RANK ligand and prevents it from binding to the receptor
What do osteocytes do?
→ They lay down bone matrix (organic material that becomes mineralised)
What is bone mineral?
→ Hydroxyapatite → Calcium and Phosphate
What do OPG and NO do?
→ Inhibit the differentiation of osteoclasts
What are the steps for activating Wnt?
→ The frizzled receptor → and the co-receptor called LRP5/6 have to interace
What is the composition of bone in %s?
→ Protein : organic osteoid matrix 25% → Mineral : 75% → Cells
What is RANK?
→ A surface receptor on pre-osteoclasts that stimulates osteoclast differentiation
What do PGE2, NO and ATP promote?
→ Differentiation of osteoblasts
How do osteocytes extend?
→ Via multiple dendrites via minute canals in the bone matrix
What is the function of bone mineral?
→ Gives bone rigidity and compressive strength
What do sclerostin, DDK and SFRP1 inhibit?
→ Inhibit the differentiation of osteoblasts
Where is trabecular bone found?
→ Near the head of the bone
How is cortical bone organised?
→ In sheet like structures → Surrounding a hollow structure called the Haversian canal
Where are osteocytes found?
→ Encased within the bone matrix
What are the 3 main types of connective tissue proper
- Areolar connective tissue
- Dense connective tissue
- Adipose connective tissue
In what gender is osteoporosis more common in?
→ Women
What is osteoporosis?
→ Loss of bone mass above a certain threshold
Broadly describe muscular tissue as a category of tissue class
- Excitable
- Specialised for contraction
What is the role of estrogen in bone remodelling?
→inhibits osteocyte apoptosis → Promotes osteoclast apoptosis → essential for skeletal health
What is the effector of the Wnt pathway?
→ beta catenin
What are the two subtypes of bone marrow cells?
→ Mesenchymal cells → Haematopoietic cells
What does process does estrogen favor?
→ Formation over resorption
What do haematopoietic stem cells give rise to?
→ Lymphoid lineage - lymphocytes → Myeloid lineage - RBC and macrophages
Where are osteoblasts found?
→ Lining the inner surface of bone
What is osteoporosis?
→ Loss of bone mass above a certain threshold
What is osteopetrosis caused by?
→ Inactivating the RANK ligand → overgrowth of bone
Role played by a skeletal muscle acting to slow or stop a movement
Antagonist
What are the 2 functions of osteoclasts?
→ Bone reabsorbing - digest old bone → Dissolve bone mineral and have enzymes to digest the organic matrix
A flat sheet like fibrous tissue that connects muscle or bone to other tissues
Aponeurosis
What do osteoclasts secrete?
→ Acid and proteases that are active in acidic environments
What are the steps for activating Wnt?
→ The frizzled receptor → and the co-receptor called LRP5/6 have to interace
What is a common bone disease?
→ Osteoporosis
How does bone remodelling occur?
→ The leading edge is where cells differentiate into osteoclasts → Behind that the new osteoblasts differentiate into new bone → As the osteoblasts lay down the new bone some of them will stay in it where they are encased in lacunae
What is the function of the organic protein matrix?
→ Gives flexibility and tensile strength
What are the 3 functions of osteoblasts?
→ Bone forming cells → Secrete osteoid collagen matrix of bone → Promote mineralisation of the osteoid
What is OPG?
→ A soluble protein produced by osteocytes
What is sclerosteosis caused by?
→ Mutation of the SOST gene → Inactivating sclerostin protein
Contraction accompanied by lengthening of a muscle
Eccentric
A connective tissue sheath that envelops each primary bundle of muscle fibers.
Perimysium
What 2 changes occur during osteoporosis?
→ Thinning of the cortical bone → Widening of the trabecular bone
What does process does estrogen favor?
→ Formation over resorption
What are the 4 types of bone cells?
→ Osteoblasts → Osteoclasts → Osteocytes → Bone marrow cells
What ratio controls osteoclast differentiation?
→ Ratio of RANK ligand to OPG
Describe simple cuboidal epithelium
In what two forms can the RANK ligand exist in?
→ Surface bounds → Soluble form that is secreted from osteocytes
How is bone continually renewed?
→ Old bone is continually resorbed and new bone is laid down → Cycle between osteoclasts digesting old bone and osteoblasts laying down new bone
Why is osteoporosis more common in women?
→ dramatic loss of estrogen due to menopause
Where is sclerostin expressed and what does it do?
→ Expressed in osteocytes → stops osteoblast differentiation
What is the life cycle of osteoclasts controlled by?
→ Apoptosis
What are the 4 types of bone cells?
→ Osteoblasts → Osteoclasts → Osteocytes → Bone marrow cells
Role played by a skeletal muscle to cause a movement
Agonist
In what two forms can the RANK ligand exist in?
→ Surface bounds → Soluble form that is secreted from osteocytes
What is the function of bone mineral?
→ Gives bone rigidity and compressive strength
What is the function of the organic protein matrix?
→ Gives flexibility and tensile strength
What is RANK?
→ A surface receptor on pre-osteoclasts that stimulates osteoclast differentiation
Describe the basic function of ‘cyte’ cells and give and example
“Cyte” cells
Mature form; maintains/recycle/breaks down ground substance
Chondrocytes in cartilage
Osteocytes in bone
What is the RANK ligand produced by and what does it do?
→ Produced by pre-osteoblasts, osteoblasts and osteocytes → binds to RANK and stimulates osteoclast differentiation
What do mesenchymal stem cells make?
→ Osteoblasts and osteocytes
Where are osteoblasts found?
→ Lining the inner surface of bone
Where is trabecular bone found?
→ Near the head of the bone
Name the four categories into which tissues are classified
- Nervous
- Muscular
- Epithelial
- Connective
Where is sclerostin expressed and what does it do?
→ Expressed in osteocytes → stops osteoblast differentiation
The ability to contract or shorten
Contractility
Describe simple epithelia
- Three main types
- One layer of cells
- Basement membrane
- Different shape nuclei
- Basal/apical specialisation
- No blood vessels
What are the 3 functions of osteoblasts?
→ Bone forming cells → Secrete osteoid collagen matrix of bone → Promote mineralisation of the osteoid
A wave of symmetrical squeezing of the digestive tract walls that occur during digestion
Peristalsis
What is the function of the lacunocanalicular system?
→ Maintains communication between the bone surface and blood vessels
What is osteopetrosis caused by?
→ Inactivating the RANK ligand → overgrowth of bone
Describe the basic function of clast cells, and give and example
“Clast” cells – break down of connective tissue
- Osteoclast in bone
- Chondroclast in cartilage
How do osteocytes extend?
→ Via multiple dendrites via minute canals in the bone matrix
What is the Wnt pathway regulated by?
→ DKK and Sclerostin
What is a rare bone disease?
→ Osteomalacia
What is the function of trabecular bone?
→ Makes bone lighter
What does the RANK receptor binding promote?
→ osteoclast differentiation
What do mesenchymal stem cells make?
→ Osteoblasts and osteocytes
What do osteoclasts secrete?
→ Acid and proteases that are active in acidic environments
A fine protective sheath of connective tissue around a skeletal muscle fiber
Endomysium
What are the function of Haversian canals?
→ Allow for blood vessel penetration
What are the 3 phases of bone remodelling?
→ Activation : promotion of differentiation of new osteoclasts → Resorption : duration of osteoclast activity → Reversal : osteoclast apoptosis, terminating activity
What do osteoclasts look like?
→ They are large and multinucleate
What are the function of Haversian canals?
→ Allow for blood vessel penetration
A bundle of muscle fibers
Fascicle
The ability to respond to a stimulus
Irritability
What are the two basic classifications of epithelial tissue
Broadly describe nervous tissue as a category of tissue class
- Excitable
- Specialised for rapid signal conduction
Broadly describe epithelial tissue as a category of tissue class
- Cover organs, form glands
- Protect, secrete and absorb
What ratio controls osteoclast differentiation?
→ Ratio of RANK ligand to OPG
What do osteocytes do?
→ They lay down bone matrix (organic material that becomes mineralised)
What is a protease that osteoclasts secrete?
→ Cathepsin K
What are lacunae?
→ cell sized holes within the bone matrix
The outermost sheath of connective tissue that surrounds a skeletal muscle
Epimysium
What is the effector of the Wnt pathway?
→ beta catenin
What do sclerostin, DDK and SFRP1 inhibit?
→ Inhibit the differentiation of osteoblasts
What does the RANK ligand promote?
→ Promotes the differentiation of osteoclasts
What is bone mineral?
→ Hydroxyapatite → Calcium and Phosphate
Describe simple columnar epithelium
What does OPG do?
→ Acts as an antagonist → binds to RANK ligand and prevents it from binding to the receptor
What do osteoclasts look like?
→ They are large and multinucleate
What are the 3 phases of bone remodelling?
→ Activation : promotion of differentiation of new osteoclasts → Resorption : duration of osteoclast activity → Reversal : osteoclast apoptosis, terminating activity
What are osteocytes?
→ Terminally differentiated osteoblasts
What are the repeating units of cortical bone?
→ Osteons
What is delayed skeletal growth in men linked to?
→ Aromatase deficiency
What is the function of the lacunocanalicular system?
→ Maintains communication between the bone surface and blood vessels
What are the repeating units of cortical bone?
→ Osteons
What is a rare bone disease?
→ Osteomalacia
A type of contraction that involves no change in muscle length
Isometric
How does bone remodelling occur?
→ The leading edge is where cells differentiate into osteoclasts → Behind that the new osteoblasts differentiate into new bone → As the osteoblasts lay down the new bone some of them will stay in it where they are encased in lacunae
In what gender is osteoporosis more common in?
→ Women
What is the composition of bone in %s?
→ Protein : organic osteoid matrix 25% → Mineral : 75% → Cells
What is the role of estrogen in bone remodelling?
→inhibits osteocyte apoptosis → Promotes osteoclast apoptosis → essential for skeletal health
A type of contraction that results in shortening of a muscle
Concentric
What are the 3 factors that control bone remodelling?
→ Load bearing exercise → Cytokines and local signals → Endocrine
The delicate membrane surrounding each striated muscle fiber
Sarcolemma
Broadly describe connective tissue as a category of tissue class
•Support, bind and protect organs
What is the Wnt pathway regulated by?
→ DKK and Sclerostin
Why is osteoporosis more common in women?
→ dramatic loss of estrogen due to menopause
Describe the basic function of ‘blast’ cells and give an example
“Blast” cells
- Immature form; mitotically active; secrete ground substance and fibers
- Fibroblasts in connective tissue proper
- Chondroblasts in cartilage
- Osteoblasts in bone
