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DAT Bio > Bone > Flashcards

Bone Flashcards

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Biology 101 flashcards
1
Q

What are the characteristics of bone?

A
  • Bone is the most rigid of connective tissues
  • It is one of the hardest tissues in the body
  • It is a dynamic tissue. It constantly changes shape to deal with the stresses placed on it.
  • We have 206 bones. (Enamel = hardest substance in body)
  • Functions in support and protection of internal organs
  • Is the principle reservoir for Ca++, PO43-, Na+, and Mg++
  • Contains homopoietic bone marrow which makes blood cells
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2
Q

What is the percentage breakdown of subtypes of bone and their characteristics?

A

Cortical bone

  • 80% of bone mass
  • Dense, compact bone
  • Outer layer covered by periosteum ( a dense collagenous connective tissue covering diaphysis of many bones)

Cancellous bone

  • 20% of bone mass
  • Spongy Bone found at the ends of long bones
  • Highly vascular
  • Inner layer spongy and light
  • Provides space for the bone marrow where RBCs, WBCs, and platelets are produced.

NB: All bones contain both types of bone, but differ in percentages.

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3
Q

Epiphysis

A

End segment of a long bone, contains a cartilaginous layer that allow long bones to grow. Once in adulthood the plates close and there is no more growth.

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4
Q

Metaphysis

A

Region that contains the growth plate.

Columns of spongy tissue is found

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5
Q

Diaphysis

A

Body or shaft of the bone

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6
Q

Medullary Cavity

A

The Medullary cavity is also called the Marrow cavity.

Enclosed by cortical bone, this is where the marrow resides.

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7
Q

What are the two types of bone marrow?

A

Red Marrow

Yellow Marrow

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8
Q

What is red marrow?

A
  • Virtually all bones at birth have this.
  • Tissue that makes blood and blood cells are here (homopoietic)
  • At adolescence it’s confined to the axial skeleton (skulls, ribs, vertebrae, and sternum)
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9
Q

What is yellow marrow?

A
  • Fat tissue

- May convert to red marrow if blood loss is severe

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10
Q

What is the structure of bone?

A
  • Inorganic Matrix
  • Calcium Phosphate [Ca3(PO4)2]
  • Hydroxyapatite crystals [Ca10(PO4)6 (OH)2]
  • 99% of the body’s Ca++ is stored as hydroxyapitite crystals
  • Organic Matrix
  • Collagen
  • Ground Substance (contains many glycoproteins)

Bottom line for DAT:
The distinguishing feature of bone is ground substance and its extracellular matrix of collagen

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11
Q

What does the axial skeleton consist of?

A
  • Skull,
  • Sternum
  • Ribs,
  • Vertebrae

Think the body’s axis

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12
Q

What does the appendicular skeleton consist of?

A
  • Bones of pelvic and pectoral girdle like arms, legs, feet, etc.

Think the body’s appendages and everything that facilitates the movements of appendages. Pelvis, collar bone, etc.

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13
Q

What are ligaments?

A

Dense regular tissue that connects bone to bone

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14
Q

What are tendons?

A

Dense regular tissue that connects bone to muscle

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15
Q

What are joints?

A

Areas of contact, or areas near contact between two points

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16
Q

What are the types of bone at a microscopic level?

A

Primary bone

Secondary bone

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17
Q

What is primary bone?

A

At a microscopic level

  • temporary bone usually replaced in adults
  • first bone to form during fetal development and during bone repair
  • random collagen arrangement
  • present around tooth sutures always
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18
Q

What is secondary bone

A

At a microscopic level

  • Permanent bone
  • What most adult bone is
  • more ordered collagen arrangement in the extracellular matrix.
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19
Q

What is the Haversian System?

A

The Haversian system is also called an Osteon

  • Represents the functional unit of much of compact bone.
  • Contains
  • Osteocytes
  • Lacunae
  • Canaliculi
  • Concentric Lamellae
  • Haversian Canal

Pneumonic:
Oysters in the Lagoon: Osteocytes in the Lacunae
Bone canals: Canaliculi
Lamination: Lamellae
Aversion Canal: Haversian Canal is in the center trying to get away from everything.

20
Q

What are Lacunae?

A
  • Spaces in bone occupied by bone cells called osteocytes

- One osteocyte occupies each lacuna

21
Q

What are Canaliculi?

A
  • Cavities seen within bone matrix, serve as passages for substances and nutrient between the blood vessels and bone cells
22
Q

What are Lamellae?

A
  • Concentric rings of matrix surrounding the Haversian canal
23
Q

What is an osteocyte?

A
  • Its a bone cell.
  • Formed when an osteoblast becomes embedded in the matrix it secretes.
  • Found in a lacuna
  • Has projections called canaliculi and can communicate with other osteocytes through these canals via gap junctions
  • Does NOT undergo Mitosis
24
Q

What is the Haversian Canal?

A

It’s a large canal found in the middle of an osteon (Haversian System)

Nerves, Blood, and lymph vessels travel through here.

25
Q

What are Volkmann’s canals?

A
  • These are the connecting canals of compact bone.
  • They connect multiple Haversian canals together and help innervate and bring nutrients throughout compact bone
  • Filled with nerves, blood, and lymph vessels.
26
Q

What is an osteoblast?

A
  • Found at the surface of bone
  • Mononucleated cells that build bone
  • Do NOT undergo Mitosis
  • They are fibroblasts (They make collagen)
  • They synthesize much of the organic matrix of the bone, thus exhibit an abundant amount of rough ER and Golgi
  • Arise from Mesenchymal stem cells
  • Become an osteocyte when they become trapped in the extracellular matrix they create.
27
Q

What is a mesenchymal stem cell?

A
  • It is an embryonic connective tissue cell derived from mesoderm.
  • It is a stem cell that gives rise to a lot of different cell types including:
  • Osteoblasts
  • Myocytes (muscle cells)
  • Chondrocytes (cartilage cells)
  • Adipocytes (fat cells)
  • They also make growth factors
28
Q

What is an osteoclast?

A
  • A member of the monocyte / macrophage family.
  • They break down bone (bone resorption)
  • Once they are finished they often die by apoptosis
  • These multinucleated cells have abundant lysosomes and mitochondria and are very large and motile
  • They occupy shallow depressions called Howship’s lacunae that identify areas of bone reabsorption
  • Lysosomal enzymes such as gelatinase and collagenase are secreted by these cells which degrade the bone.
  • Does NOT undergo Mitosis
29
Q

What bone cells don’t undergo Mitosis?

A

This is a common DAT question

  • Osteoclast
  • Osteoblast
  • Osteocyte
30
Q

What is an osteoprogenitor cell?

A
  • It is derived from a primitive stem cell (mesenchymal) and differentiates into osteoblasts and osteocytes.
  • Found in the marrow, periosteum, and within the marrow cavity
31
Q

What is coupling?

A

An important DAT concept to understand

  • Osteoclasts break down some bone to “excavate” the area to form an absorption cavity.
  • Bone resorption stops
  • Osteoblasts now take over and build new bone.
  • This process of bone breakdown and rebuilding is called coupling
  • The process is important to help maintain calcium homeostasis as well as building adaptations to mechanical pressures exerted on bones.
32
Q

How does coupling differ in young people.

A

As you’re still growing, bone growth exceeds resorption. Once the growth plates ossify then normal coupling proceeds with maintaining homeostasis of Ca++

33
Q

What is Acromegaly?

A

Excess growth hormone causes an increase in bone deposition without normal breakdown.

Bones become very thick, especially in the face

34
Q

What is Osteoporosis?

A
  • Osteporosis is a decrease in bone mass, which gets worse as estrogen levels decline.
  • Estrogen therapy could help this.
  • Bones become very fragile as osteoclastic activity exceeds bone deposition, thus making bones easy to break
  • Not getting enough calcium contributes to this issue, because bone is broken down for Ca++ and not built back up properly
35
Q

How are the thyroid and parathyroid involved in Ca++ homeostasis?

A

Decrease in Ca++

  • When Ca++ levels decrease, the parathyroid gland releases parathyroid hormone which binds to hormone receptors on osteoblasts and causes them to stop building bone.
  • The Osteoblasts then secrete Osteoclast-Stimulating Factor, which induces Osteoclast formation and they start breaking down bone and releasing Ca++ into the body.

Increase in Ca++

  • When Ca++ levels increase, the thyroid gland secretes calcitonin which binds to hormone receptors on osteoclasts, inhibiting them from breaking down any more bone.
  • Osteoblasts start using the Ca++ to build more bone mass

Summary:

Low Ca++: Parathyroid -> Parathyroid Hormone -> Osteoblast Stop -> Osteoclast Stimulating Factor from Osteoblast -> Osteoclast GO!

High Ca++: Thyroid -> Calcitonin -> Osteoclast stop

36
Q

Describe Cartilage

A
  • Cartilage is a specialized connective tissue
  • Does not contain blood vessels, nerves, or lymphatics, but gets its nourishment from blood vessels of surrounding tissues by diffusion through the extracellular matrix.
  • Inorganic phase is like bone. It contains hydroxyapatite
  • Organic structure is very different from bone. It contains 80% water and the other 20% collagen and proteoglycans.
  • Cells called chondrocytes occupy small cavities called lacunae.
  • It’s surrounded by a dense fibrous connective tissue called the perichondrium (around cartilage).
  • Since it has no blood supply, it has a very slow rate of mitotic activity, and if damaged, heals slowly and with difficulty.
37
Q

What are Chondrocytes?

A
  • They are the cellular unit of cartilage

- They make collagen and molecules needed by the extracellular matrix

38
Q

What are the three different types of cartilage?

A

The three types of cartilage are:

  • Hyaline Cartilage
  • Elastic Cartilage
  • Fibrocartilage
39
Q

What is hyaline cartilage?

A

Hyaline cartilage is the most abundant type of cartilage

  • We find it in the:
  • Nose
  • Larynx
  • Part of the ribs
  • Trachea
  • Bronchi
  • Epiphyseal Plate
  • Reduces friction
  • Shock Absorber
  • Aids in Bone Movement
40
Q

What is Elastic Cartilage

A
  • Elastic Cartilage is found in the pinna of the ear (outer ear) and the epiglottis (part of the larynx)
  • Principle protein is elastin
  • Allows for repeated bending
41
Q

What is fibrocartilage?

A
  • Intervertebral discs, pubic symphysis, menisci, and Temporomandibular joint
  • Has tons of both Type I and Type II collagen fibers (only type that has both)
42
Q

What is cartilage derived from?

A

It’s derived from mesenchyme, a stem cell that also can turn in to osteocytes and many other things.

It’s growth is dependent on somatotropin (growth hormone)

43
Q

What are the arm bones

A
  • Humerus
  • Radius
  • Ulna
44
Q

What are the leg bones?

A
  • Femur
  • Tibia
  • Fibula
45
Q

What are the foot and hand bones?

A

Hand: Carpals
Foot: Tarsals

46
Q

What are the vertebral bones?

A

Lumbar, Thoracic, Vertebral, Sacrum, coccyx

DAT Bio (46 decks)

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