Anatomy of Bones: Structure, Function, and Growth, Exams of Nursing

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ANAT 101 STUDY GUIDE

Q & A

1. Identify the features of a typical long bone.
2. Diaphysis (bone shaft)
3. 2 epiphyses (both ends of the bone at the joints)
4. 2 metaphyses (region between diaphysis and epiphysis)
5. Articular cartilage covering both epiphyses
6. Periosteum (connective tissue surrounding the diaphysis)
7. Medullary cavity (hollow space within diaphysis)
8. Endosteum (thin membrane lining the medulary cavity)
9. Describe the structure and function of both the periosteal and endosteum layer of bone.
10. Periosteum: circulation and nerves, bone growth and repair, joint capsule, ligament, tendon attachment (sharpey's fibers)
11. Endosteum: bone growth, repair, and remodeling
12. Bone is considered connective tissue. Describe the cells, ground substance and fibers that comprise bone.
13. Cells: a. Osteoprogenitor cells (bone stem cells that can diferentiate) b. Osteoblasts (build bone by secreting matrix) c. Osteocytes (mature bone cells) d. Osteoclasts (remodel bone and cause them to release calcium)
14. Extracellular Matrix: (same in compact and spongy bone) a. Ground substance:

i. Hydroxyapatite: calcium phosphate, calcium hydroxide - resists compressive forces ii. GAGs iii. Water b. Fibers: collagen fibers

1. Describe the lineage of osteoblasts versus osteoclasts.
   1. osteoBLASTS = BUILD bone
   2. osteoCLASTS = remodel/breakdown bone
2. What are the similarities and diferences between compact bone and spongy bone? Where is each located? 1. Compact: outside, covers spongy bone a. more protection b. Support in single direction c. Dense, solid - strongest form of bone tissue d. Makes up most of the diaphysis e. Surrounds medullary canal/marrow cavity (inside diaphysis) f. Made of i. Osteon (Haversian System): basic functional unit, contains central (Haversian canal) ii. Concentric lamellae: layers of matrix iii. Interstitial lamellae iv. Circumferential lamellae 2. Spongy: inside bone

a. lightweight b. Support in many directions c. Compact bone covers it d. Open network of lamellae arranged in "random" patterns (based on stress)- makes trabeculae i. Between trabeculae are big spaces filled with either red bone marrow (in bones that produce blood cells) or yellow bone marrow (adipose tissue in others) ii. Both types of have blood supply through vessels that provide nourishment to osteocytes iii. Each trabecula consists of: ▪ Lamellae ▪ Osteocytes in lacunae ▪ Canaliculi (radiate outward from lacunae)

• Is found in: i. Interior of sesamoid bones ii. Interior of diaphysis (long part) of long bones iii. Core of epiphyses in long bones

1. What is an osteon and in which type of bone are they found? How does this difer from trabeculae?

• Osteons are found in compact bone only
• Osteons = structural unit of compact bone, aligned in same direction of stress
• Osteons are made of concentric lamellae arranges around central canal/haversian canal o Concentric lamellae = circular plates of mineralized extracellular matrix of increasing diameter that surround blood vessels and nerves in the central canal.
• can shift and change over time depending on demands of the skeleton
• Trabeculae is only in spongy vs osteons are only in compact

o But they are both made of lamellae Bone Growth and Formation o Identify the 2 types of bone formation. When or under what conditions does each occur?

• Intramembranous ossification: occurs in utero and after fractures o Bone develops directly from dense irregular connective tissue o 4 step process o Help develop flat bones of the skull, most facial bones, mandible, collarbones

2. Endochondral ossification: occurs in developing embryo and fetus o Replaces hyaline cartilage with bone in developing embryo and fetus o Ostoegenesis vs ossification
3. Osteogenesis: bone formation
4. Ossification: process of replacing other tissues with bone o Identify the 4 main steps of intramembranous ossification.
5. Develops bone from pre-existing mesenchymal cells
6. Development of ossification center: mesenchymal cells become osteoblasts - secrete osteoid - forms primary ossification center o mesenchyme cluster and diferentiate (first into osteoprogenitor cells and then into osteoblasts) - osteoblasts secrete extracellular matrix of bone until surrounded o Calcification of extracellular matrix: Osteoblasts become osteocytes and lie in lacunae - then extend cytoplasmic processes into canaliculi into diferent directions - in a few days calcium and other mineral salts are deposited and the extracellular matrix hardens (calcifies)

o Formation of trabeculae: in growth of blood vessels - red bone marrow

o as extracellular matrix hardens it develops into trabeculae that fuse with one another to form spongy bone around network of blood vessels - Connective tissue diferentiates into red bone marrow o Development of periosteum: mesenchyme condenses at periphery of bone and develops into periosteum - thin layer of compact bone replaces spongy bone but it still remains in very center - a lot of the new bone is remodeled and transformed until adulthood

• Identify the main steps of endochondral ossification. What does bone develop from during this process? o Develops from hyaline cartilage o Development of cartilage model: mesenchymal cells develop into chondroblasts, which form cartilage model o Growth of cartilage model: cell division of chondrocytes o Development of primary ossification center: bone tissue replaces most of cartilage in diaphysis o Development of medullary (marrow) cavity: bone breakdown by osteoclasts forms medullary cavity o Development of secondary ossification center: happens in epiphyses of bone o Formation of articular cartilage and epiphyseal (growth) plate: both structures made of hyaline cartilage
• Describe the steps by which bones grow longer, and the role of cartilage in this process. o by interstitial growth of cartilage on epipheseal side of epiphyseal plate & by replacement of cartilage on diaphyseal side of epiphyseal plate o Epiphyseal (growth) plate: made of four zones i. Zone of resting cartilage: closest to epiphysis - made of small chondrocytes that don't function in bone growth (aka "resting")

ii. Zone of proliferating cartilage: bigger chondrocytes stacked on top of each other - undergo interstitial growth by secreting extracellular matrix and dividing iii. Zone of hypertrophic cartilage: large, maturing chondrocytes in columns iv. Zone of calcified cartilage: mostly dead chondrocytes & extracellular matrix around them have already calcified - osteoblasts lay down bone extracellular matrix replacing calcified cartilage by endochrondral ossification (replacement of cartilage with bone) o Grows in length only on diaphyseal side of plate and not epiphyseal plate o After adolescence: epiphyseal cartilage cells stop dividing and bone replaces all remaining cartilage - epiphyseal plate fades leaving epiphyseal line

• AKA: when the all of the skeletons plates close, that's the adult structure
• ** exception: Endochondral ossification occurs in epiphyseal plates of long bones as they grow in length
• How does bone grow thicker? Under what types of conditions do you think this would occur?
• Process:
• Periosteal cells diferentiate into osteoblasts at bone surface - secrete collagen fibers and other organic molecules that form bone extracellular matrix - osteoblasts become surrounded by extracellular matrix & developing into osteocytes - forms bone ridges on either side of periosteal blood vessel
• Ridges fold together and fuse and encloses blood vessel - former periosteum becomes endosteum that lines tunnel
• Osteoblasts in endosteum deposit bone

extracellular matrix - helps form new concentric lamellae and grows in toward blood vessel (aka new osteon is created)

• Osteoblasts under periosteum deposit new circumferential lamellae -
• increasing thickness of bone & repeats
• So as it grows wider in diameter at the periosteum, osteoclasts eat away at the inner surface of the bone - even though the bone becomes wider, the medullary cavity also grows wider

• What is bone's role in the homeostasis of blood calcium?
• Bone holds 99% of body's calcium
• Never and muscle cells depend on stable Ca2+ in extracellular fluid
• Blood clotting requires Ca2+
• Lots of enzymes require Ca2+ as a cofactor (substance needed for reaction to occur) o Bone releases Ca2+ when needed (using osteoCLASTS) and absorbs it (using osteoBLASTS) when there's too much in body
• When calcium drops in blood, PTH (parathyroid hormone) is stimulated and increases number & activity of osteoclasts (increases bone resorption)
• Resorption in blood helps normalize blood calcium
• PTH slows loss of calcium in urine by promoting resorption via tubule cells
• Bone formation decreases blood calcium
• What types of activities, chemicals, etc contribute to the strength of bone, and what will contribute to bone loss? o Astronauts and non-athletes have less bone mass than athletes (much wider bones in athletes because more stress) o Good to strengthen bone before epiphyseal plate closes but helps to weight train all throughout life anyway o Becomes stronger when stressed by increased deposition of mineral salts and production of collagen fibers by osteoblasts

Introduction to the Axial Skeleton :

• Identify which bones belong to the axial versus appendicular skeleton. o 80 bones in axial skeleton, 126 in appendicular o Axial Skeleton
• Supports & protects i. Brain ii. Spinal chord iii. Organs b. Muscle attachments i. Head, neck, trunk ii. Respiration iii. Appendicular skeleton

2. Axial: a. Skull bones b. auditory ossicles (ear bones) c. hyoid bone d. ribs e. sternum (breastbone) f. bones of the vertebral column
3. Appendicular: a. Bones of the upper and lower limbs (extremities b. bones forming the girdles that connect the limbs to the axial skeleton.
4. Types of bones:
   1. Long
   2. Short
   3. Flat
   4. Irregular

5. Sesamoid
6. Sutural
7. Describe the various bone surface markings, including projections or depressions. What would cause them to form, what do they indicate?
8. Form from pulling of gravity/muscle or from stress/weight
9. 2 Types of Surface Markings a. Depressions & Openings: allows for passage of soft tissue, forms joints i. Fissure :Narrow slit between bones for passage of blood vessels or nerves. ii. Foramen: Hole for passage of blood vessels, nerves or ligaments. iii. Fossa: Shallow depression iv. Sulcus: Furrow on a bone for passage of blood vessel, nerve or tendon. v. Meatus: Tube-like opening vi. Facet: smooth, flat, slightly concave articular surface
10. Processes/Projections: projections/outgrowths that form joints, attachment points for ligaments & tendons
11. Condyle: Rounded projection with a smooth articular surface.
12. Head: Usually rounded articular process supported on a neck.
13. Crest: Prominent ridge or elongated process.
14. Epicondyle: Usually roughened projection on a condyle.
15. Line: Long, narrow ridge or border (less prominent than a crest)
16. Spinous process: sharp, slender projection
17. Trochanter: Very large projection found ONLY on the femur.
18. Tubercle: Variably sized rounded projection.

9. Tuberosity: Variably sized projection with rough, bumpy surface The Bones of the Skull :
10. Identify each of the 8 bones of the skull, the unique features highlighted in lecture, and the sutures between them.
11. Occipital bone
12. Parietal bones (2 bones)
13. Frontal bone
14. Temporal bones (2 bones)
15. Sphenoid
16. Ethmoid

• Identify the 14 bones of the face.

1. Maxillary bones (2 bones)
2. Palatine bones (2 bones)
3. Nasal Bones (2 bones)
4. Inferior nasal conchae (2 bones)
5. Zygomatic bones (2 bones)
6. Vomer
7. Mandible

• Identify the bones that make up the bony nasal septum, the orbital complex and the hard palate.

1. Nasal Septum a. Vomer bone b. Perpendicular plate of ethmoid bone o Orbital Complex a. Frontal bone b. Maxilla bone c. Lacrimal d. Ethmoid

e. Palatine f. Sphenoid g. zygomatic o Hard Palate: a. Incisive bone (premaxilla)

• Identify the bones that contain the paranasal sinuses. (help echo chambers to enhance voice & increase suface area for mucous) o Frontal o Maxillary o Sphenoid o Ethmoid The Vertebrae, Ribs and Sternum :
• Identify the number of location of the cervical, thoracic, lumbar and sacral vertebrae. How many in each group? o Cervical (7) o Thoracic (12) o Lumbar (5) o Sacral (5 fused into 1) o Coccyx

1. Identify the unique features of each vertebrae. How do they difer in size, shape, foramen, articulations, etc? It will be helpful to make a table. o Cervical a. 3 foramen total (one vertical, 2 transverse) b. Smallest body c. Slender spinous process 2. Thoracic a. 1 foramen (vertical) b. Articular facets for ribs c. Long, projects inferiorly (downward) spinous process

2. Lumbar a. 1 foramen (vertical) b. Biggest body c. Long, projects posteriorly (towards back) spinous process
3. Identify which joints allow for nodding of the head, and which allow for rotation of the head.
4. Join in between atlas (C1) and occipital bone allows for nodding up and down
5. Atlas and Axis work together to move side to side (Axis condyle fits into Axis)
6. Identify the true, false and floating ribs, and what characteristics make them so.
7. True: 1 - 7
8. False: 8 - 12 a. Floating: 11 - 12

• Identify the normal curvatures of the spine as well as abnormal curvatures. o Scoliosis (curved to side) o Kyphosis (push back on thoracic vertebrae) o Lordosis (pushed in on lumbar vertebrae) a. What happens when you wear heels a lot