Skeletal System Overview and Bone Types

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Questions and Answers

Which of the following is NOT a function of the skeletal system?

Hormone production (correct)

Protection

Mineral storage

Movement

At what age does the human skeleton typically complete its hardening process?

25 years (correct)

18 years

30 years

21 years

What classification of bone is characterized by having small open spaces resembling a sponge?

Long bone

Compact bone

Flat bone

Spongy bone (correct)

Which of the following correctly describes the classification of bones by position?

Axial and appendicular skeletons Signup and view all the answers

What is a key role of bone tissue related to minerals in the blood?

Maintaining mineral concentration Signup and view all the answers

How many bones are there in the adult human axial skeleton?

80 bones Signup and view all the answers

Which class of bones is NOT part of the long bone classification?

Patella Signup and view all the answers

Which of the following accurately describes compact bone?

It has a smooth appearance with no apparent spaces. Signup and view all the answers

Which vitamin is crucial for the intestinal absorption of calcium?

Cholecalciferol (Vitamin D) Signup and view all the answers

What is the active form of cholecalciferol called?

Calcitriol (1,25-dihydroxyvitamin D3) Signup and view all the answers

What effect does parathyroid hormone (PTH) have on blood calcium levels?

It regulates and typically increases blood calcium concentrations. Signup and view all the answers

Which statement is true regarding bone health as people age?

Bone becomes more brittle and weaker. Signup and view all the answers

What common fractures are observed in older adults, particularly in menopausal women?

Hip and vertebral compression fractures Signup and view all the answers

Which type of bone is characterized as being typically longer than wide and used for levers and weight bearing?

Long bones Signup and view all the answers

What is the primary characteristic of short bones?

They are generally cube-shaped. Signup and view all the answers

Which type of bone is typically thin, flattened, and usually curved?

Flat bones Signup and view all the answers

What best describes irregular bones?

They have an irregular shape. Signup and view all the answers

What is the function of sesamoid bones?

They form within tendons and ligaments. Signup and view all the answers

Which of the following is NOT a characteristic of long bones?

Contain mostly spongy bone Signup and view all the answers

Which bone shape is primarily associated with boxy, lightweight structures?

Short bones Signup and view all the answers

Which of the following is an example of a flat bone?

Ribs Signup and view all the answers

What is the function of the zone of resting cartilage?

It anchors the epiphyseal plate to the epiphysis. Signup and view all the answers

Which zone is characterized by cells that are undergoing mitosis?

Zone of proliferating cartilage Signup and view all the answers

What follows the zone of hypertrophic cartilage in the growth at the epiphyseal plate?

Zone of calcified cartilage Signup and view all the answers

What characterizes the cells in the second layer of the epiphyseal plate?

They are many rows of young cells undergoing mitosis. Signup and view all the answers

What is the primary ossification center in endochondral ossification?

The middle of the shaft Signup and view all the answers

What is the primary role of the zone of calcified cartilage?

To facilitate the transition to ossified bone. Signup and view all the answers

Which of the following describes a distinction between endochondral and intramembranous ossification?

Intramembranous ossification does not develop an intermediate cartilage stage. Signup and view all the answers

At which location in the bone structure would you primarily find the zone of resting cartilage?

Closest to the epiphysis. Signup and view all the answers

During the ossification process, how is damaged bone primarily repaired?

Through remodeling and repair mechanisms Signup and view all the answers

At what stage in fetal development does the skeleton begin to form?

At six weeks Signup and view all the answers

Which zone is NOT directly involved in the growth of the cartilage?

Zone of resting cartilage Signup and view all the answers

What type of bone develops from fibrous membranes?

Membranous bone Signup and view all the answers

What type of tissue is primarily found in the epiphyseal plate?

Hyaline cartilage Signup and view all the answers

What is the sequence of events in endochondral ossification?

Cartilage model, ossification, bony collar, marrow appearance Signup and view all the answers

Which is a reason for bone remodeling?

In response to stress of daily life Signup and view all the answers

Which part of the bone forms articular cartilage and the epiphyseal plate during ossification?

Secondary ossification centers Signup and view all the answers

Study Notes

Skeletal System Organization

Axial skeleton consists of 80 bones, Appendicular skeleton consists of 126 bones
Fully mature human skeleton contains 206 bones
Skeleton fully hardens by age 25

Bones and Bone Tissue

Bone tissue functions to maintain and repair bones, and as a reserve pool of calcium, magnesium and phosphorus
Bone classification depends on gross and microscopic structure
Compact bone is dense with a smooth appearance
Spongy bone contains many small open spaces

Bone Classification

Long bones: Longer than they are wide, have a shaft with heads at both ends, used for levers and weight bearing, mostly compact bone
- Examples: Femur, Humerus
Short bones: Generally cube-shape, boxy and lightweight, non-weight bearing, mostly spongy bone
- Examples: Carpals, Tarsals
Flat bones: Thin and flattened, usually curved, thin layers of compact bone surrounding a layer of spongy bone
- Examples: Skull, Ribs, Sternum
Irregular bones Irregular shape, not categorized into other bone types
- Examples: Vertebrae and Pelvis
Sesamoid bones Small bones that form within tendons and ligaments
- Example: Patella (kneecap)
Wormian bones (sutural) Small, irregular bones found within sutures of the skull

Parts of a Long Bone

Diaphysis is the shaft of the long bone
Epiphyses are the ends of the long bone
Epiphyseal plate is the growth plate of the long bone

Bone Formation

Ossification is the process of bone formation, growth, remodeling and repair
Ossification occurs in four situations:
- Initial formation of bones in the embryo and fetus
- Bone growth in children and adolescents
- Remodeling of stressed bones
- Repair of damaged bone

Bone Formation Processes

Endochondral ossification: Bone development from cartilage
- Cartilage model is prepared by chondroblasts
- A bony collar forms as model enlarges
  - Ossification begins in the middle of the shaft (primary ossification center)
- Narrow space enlarges and bone marrow appears
- Secondary ossification centers appear at the ends of long bones
  - Articular cartilage and epiphyseal plate form
Intramembranous ossification: Bone development from fibrous membranes
- No intermediate stage develops
- First layer of cells are closest to the epiphysis end
- Second layer of cells are undergoing mitosis

Growth at the Epiphyseal Plate

Zone of resting cartilage anchors the epiphyseal plate to the epiphysis
Zone of proliferating cartilage contains young cells undergoing mitosis
Zone of hypertrophic cartilage contains mature cells
Zone of calcified cartilage contains ossified bone of diaphysis

Calcium Homeostasis

Body is unable to synthesize calcium, it must be consumed through diet and absorbed through the intestine
Inadequate absorption of calcium requires cholecalciferol (vitamin D)
Kidneys convert cholecalciferol into its active form calcitriol (1,25-dihydroxyvitamin D3)

Parathyroid Hormone (PTH)

PTH regulates blood calcium, and ultimately increases blood calcium concentrations
If blood calcium rises above set point, parathyroids reduce PTH secretion, and blood calcium returns to set point

Blood Cells and Bone

Blood cells are produced in the red bone marrow

Lifespan Changes in Bone

Decrease in height begins around age 30
Calcium levels fall, bones become brittle
Osteoclast outnumber osteoblasts
Spongy bone weakens before compact bone
Bone loss is rapid in postmenopausal women
Hip fractures are common, as are vertebral compression fractures

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Description

Explore the fascinating organization of the skeletal system, which includes the axial and appendicular skeletons as well as key information about bone types. Understand the structure and function of different bones, including long, short, flat, and irregular bones. This quiz will test your knowledge of bone classification, composition, and growth.