Functions and Divisions of the Skeletal System

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Questions and Answers

What is one primary function of the skeletal system?

Temperature regulation

Chemical digestion

Hormone production

Mineral storage (correct)

Which part of a long bone is responsible for housing the marrow?

Metaphysis

Diaphysis (correct)

Articular cartilage

Epiphysis

Which shape classification does a vertebrae fall under?

Irregular Bone (correct)

Flat Bone

Short Bone

Long Bone

What type of bone tissue is primarily found in the ends of long bones?

Cancellous (Spongy) Bone Signup and view all the answers

In adults, which part of the bone primarily contains red bone marrow?

Spongy Bone Signup and view all the answers

What is the primary organic component of bone tissue?

Collagen fibers Signup and view all the answers

Which type of bone cell is responsible for the breakdown of bone?

Osteoclasts Signup and view all the answers

What is the role of osteocytes in bone tissue?

Maintain bone matrix Signup and view all the answers

Which process involves the transformation of mesenchyme directly into bone?

Intramembranous ossification Signup and view all the answers

What primarily enters the diaphysis of long bones?

Nutrient arteries Signup and view all the answers

Which component constitutes the majority of the inorganic part of bone?

Hydroxyapatite crystals Signup and view all the answers

What type of bone is produced by endochondral ossification?

Long bones Signup and view all the answers

Where are blood and nerves primarily found in bone?

In the periosteum Signup and view all the answers

What is the role of chondrocytes during primary ossification?

They enlarge, calcify, and then die. Signup and view all the answers

What structure forms over the dead cartilage during primary ossification?

Bone collar of compact bone Signup and view all the answers

Where does secondary ossification primarily occur?

In the epiphyses Signup and view all the answers

What is the primary function of osteoclasts in bone remodeling?

To destroy spongy bone and create cavities Signup and view all the answers

What is appositional growth primarily responsible for?

Increasing the girth or diameter of bones Signup and view all the answers

What characterizes the periosteum layer of bone?

It has an outer dense fibrous connective tissue layer. Signup and view all the answers

Which cells are involved in both bone deposition and resorption?

Osteoblasts and osteoclasts Signup and view all the answers

What is a key requirement for proper bone remodeling?

Regular stress on the bone Signup and view all the answers

Which type of fracture involves damage to the epiphyseal plate and may disrupt bone growth?

Epiphyseal Fracture Signup and view all the answers

What is the first step in the fracture repair process?

Hematoma Formation Signup and view all the answers

Which of the following conditions is characterized by excess growth hormone (GH) after closure of growth plates?

Acromegaly Signup and view all the answers

What kind of bone fracture is classified as both complete and open?

Compound Fracture Signup and view all the answers

Which of the following disorders is associated with vitamin D deficiency in children?

Rickets Signup and view all the answers

What effect does mechanical stress have on osteoblasts?

Stimulates osteoblast activity Signup and view all the answers

Which hormone is responsible for lowering blood calcium levels?

Calcitonin Signup and view all the answers

What is a key role of calcium in the body?

Facilitating muscle contraction Signup and view all the answers

At what age does the epiphyseal plate typically close for females?

13-15 years Signup and view all the answers

Which vitamin is necessary for the synthesis of collagen proteins?

Vitamin C Signup and view all the answers

What risk factor for osteoporosis is associated with age?

Decreased estrogen post-menopause Signup and view all the answers

Which of the following hormones raises blood calcium levels?

Parathyroid Hormone Signup and view all the answers

What lifestyle factor is linked to osteoporosis risk?

Low body mass Signup and view all the answers

Study Notes

Functions of the Skeletal System

Support and protect the body
Enable movement
Store minerals (calcium and phosphate)
Participate in blood cell production (red bone marrow)
Store fat

Divisions of the Skeletal System

Axial Skeleton: Forms the central axis of the body, including the skull, vertebral column, and rib cage
Appendicular Skeleton: Consists of the bones of the limbs and their girdles (shoulder and pelvic girdles)

Bone Shapes

Sutural bones: Small, irregular bones found within sutures (joints) of the skull
Long bones: Longer than they are wide (e.g., femur, humerus)
Flat bones: Thin and flattened, often curved (e.g., skull bones, ribs, sternum)
Short bones: Roughly cube-shaped (e.g., carpals, tarsals)
Irregular bones: Bones with complex shapes (e.g., vertebrae, facial bones)
Sesamoid bones: Small round bones embedded in tendons (e.g., patella)

Parts of a Long Bone

Epiphyses: The expanded ends of a long bone, covered with articular cartilage
Metaphyses: The regions between the diaphysis and epiphyses, containing the epiphyseal plate/line
Diaphysis: The shaft or central region of a long bone
- Periosteum: A tough fibrous membrane that surrounds the diaphysis, with collagen fibers that attach it to the bone
- Compact bone: Dense, hard outer layer of the diaphysis
- Endosteum: A thin membranous layer that lines the medullary cavity
- Medullary cavity: The hollow space within the diaphysis, containing bone marrow

Gross Anatomy: Flat/Short Bones

Compact bone: Outer layer
Spongy (Cancellous) bone: Inner layer, also known as diploe
Red bone marrow: Found within spongy bone, responsible for hematopoiesis (blood cell production)

Bone Matrix and Chemistry

Organic component (33-35%): Primarily collagen fibers, proteoglycans, glycosaminoglycans, glycoproteins, and osteocalcin
Inorganic component (65-67%): Mainly hydroxyapatite crystals (calcium salts and potassium), along with bicarbonate, magnesium, phosphate, and sodium salts

Blood and Nerves to Bone

Periosteum: Contains a network of blood vessels and nerves, especially for short, flat, irregular, and sesamoid bones
Diaphysis: Received blood supply from nutrient arteries entering through the nutrient foramen
Epiphyses: Supplied by small blood vessels entering through small holes and nutrient arteries

Bone Cells

Osteoprogenitor cells: Undifferentiated cells give rise to osteoblasts
Osteoblasts: Bone-building cells, responsible for depositing new bone matrix
Osteocytes: Mature bone cells, maintain bone matrix
Osteoclasts: Bone-destroying cells, responsible for bone resorption and remodeling

Bone Production and Resorption

Osteoblasts: Deposit new bone matrix.
Osteocytes: Maintain bone.
Osteoclasts: Breakdown bone matrix to release calcium, contributing to bone remodeling.

Compact Bone Histology

Consists of osteons (Haversian systems): concentric rings of lamellae (layers) containing osteocytes, surrounding a central canal containing blood vessels and nerves.
Canaliculi: Tiny channels that connect lacunae (spaces housing osteocytes) and allow for communication and nutrient exchange.

Spongy (Cancellous) Bone Histology

Composed of trabeculae: interconnected bony plates that form a lattice-like structure.
Bone marrow: fills spaces within the trabeculae.

Bone Development: 2 Routes

Intramembranous ossification: Direct formation of bones from mesenchyme, occurs in flat bones (skull, clavicle)
Endochondral ossification: Replacement of hyaline cartilage by bone, responsible for the formation of long bones.

Intramembranous Ossification

Primary Ossification: Begins in the center of the bone and moves outwards
Secondary Ossification: Begins in the epiphyses of long bones, after birth.

Endochondral Ossification

Hyaline cartilage acts as a template for bone formation.
Chondrocytes enlarge, calcify, die, and degenerate.
Perichondrium becomes the periosteum.

Appositional Growth

Increase in bone diameter
New bone deposited by osteoblasts in the periosteum and endosteum.

Periosteum and Endosteum

Periosteum: Outer dense fibrous membrane covering the bone, contains osteoprogenitor cells.
Endosteum: Thin, inner membranous layer lining bone marrow cavities, contains osteoprogenitor cells.

Bone Remodeling

Continuous process of bone deposition (by osteoblasts) and resorption (by osteoclasts).
Ensures bone strength and adaptation to mechanical stress.
Spongy bone: Replaced by compact bone.

Hormonal Regulation of Bone Growth

Growth Hormone (GH): Stimulates bone growth.
Thyroxine (TH): Influences bone growth, working with GH.
Sex hormones (testosterone and estrogen): Promote bone growth and contribute to the closure of epiphyseal plates.
Progesterone: Influences bone growth, working with estrogen.
Calcitonin: Inhibits bone resorption.
Parathyroid Hormone (PTH): Stimulates bone resorption.

Metabolic Role of Bones

Calcium: Involved in many bodily functions, including muscle contraction, nerve function, and enzyme activity.
Hormonal control of blood calcium:
- PTH: Raises blood calcium levels by stimulating bone resorption.
- Calcitonin: Lowers blood calcium levels by inhibiting bone resorption.

Epiphyseal Plate and Line

Epiphyseal plate: Layer of hyaline cartilage responsible for lengthwise bone growth.
Epiphyseal line: Forms when the epiphyseal plate closes, marking the end of bone growth.

Vitamins, etc. for Bone Growth

Calcium: Essential for bone mineralization.
Vitamin C: Required for collagen synthesis.
Vitamin D: Aids in calcium absorption and prevents calcium loss through the kidneys.
Vitamin K: Aids in the production of calcium-binding glycoproteins.
Protein: Required organic matrix synthesis.

Osteoporosis

Risk factors:
- Age, genetics (runs in families), gender (female), race, nutrition (low calcium intake, low vitamin D intake, high soda consumption), lack of exercise, certain medications.
Causes:
- Decreased bone density and weakening of bone tissue, increasing the risk of fractures.

Other Bone Weakening Disorders

Rickets: A condition caused by vitamin D deficiency in children, resulting in soft and weakened bones.
Osteomalacia: A condition caused by vitamin D deficiency in adults, resulting in soft and weakened bones.
Paget's Disease: A condition characterized by abnormal bone remodeling and disorganized bone structure.

Bone Fracture Types

Incomplete fracture: A crack in the bone that does not completely break it.
Complete fracture: A bone break that completely severs the bone.
Displaced fracture: A bone break where the bone fragments are out of alignment.
Non-displaced fracture: A bone break where the bone fragments remain in alignment.
Closed (simple) fracture: A bone break that does not break the skin.
Open (compound) fracture: A bone break that breaks the skin.

Fracture Repair

Hematoma Formation: Blood clots form at the fracture site.
Fibrocartilage Callus Formation: Soft callus forms, composed of cartilage and fibrous tissue.
Bony Callus Formation: Hard callus forms, composed of bone tissue.
Remodeling: The bony callus is remodeled to resemble the original bone.

Abnormal Growth

Gigantism: Excessive growth hormone (GH) production, resulting in excessive bone growth.
Pituitary Dwarfism: Deficiency in GH production, resulting in abnormally short stature.
Acromegaly: Excessive GH production after epiphyseal plates have closed, causing bone growth in face, hands, and feet.
Achondroplasia: A genetic disorder characterized by abnormal cartilage growth, resulting in dwarfism.
Marfan Syndrome: A genetic disorder caused by excessive cartilage growth, leading to long limbs, a tall stature, and other skeletal abnormalities.

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Description

Explore the essential functions and divisions of the skeletal system in this quiz. Learn about the axial and appendicular skeletons, as well as the different shapes of bones in the human body. Test your knowledge on the structural aspects and roles of bones.