Skeletal System Overview

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Questions and Answers

What is the primary structural unit of compact bone?

Canaliculus

Osteon (correct)

Lacuna

Trabeculae

Where is spongy (cancellous) bone tissue primarily located?

At the epiphyses of long bones and center of other bones (correct)

At the diaphysis of long bones

Within the medullary cavity of bones

On the outer surface of long bones

What role do osteoclasts play in bone tissue?

They form bone matrix

They remodel bone by removing existing bone (correct)

They maintain the bone matrix

They store marrow within bone cavities

Which process describes the formation of bone within connective tissue membranes?

Intramembranous ossification Signup and view all the answers

What is the purpose of lamellae in compact bone?

Form rings of bone matrix Signup and view all the answers

What characterizes the primary ossification center in endochondral ossification?

Formation in the diaphysis of long bones Signup and view all the answers

What is the role of canaliculi in compact bone?

Connect osteocytes to other osteocytes Signup and view all the answers

Which of the following statements about trabeculae in spongy bone is true?

They create spaces that contain bone marrow Signup and view all the answers

What is the role of osteoblasts in bone growth in width?

They deposit new bone matrix on existing bone. Signup and view all the answers

During endochondral ossification, what happens to chondrocytes in the epiphyseal plate?

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

Which statement best describes bone remodeling?

It involves the continuous removal and deposition of bone. Signup and view all the answers

What structure forms first in the sequence of bone repair?

Fibrous callus Signup and view all the answers

What is the primary function of the primary ossification center during bone development?

To create the diaphysis of the bone. Signup and view all the answers

Which process is responsible for the increase in height during bone growth?

Endochondral ossification Signup and view all the answers

What is the final fate of the original cartilage model in endochondral ossification?

It becomes nearly fully ossified. Signup and view all the answers

Which cells are primarily responsible for breaking down bone during remodeling?

Osteoclasts Signup and view all the answers

What is the primary function of the frontal bone?

Comprises the anterior part of the cranium Signup and view all the answers

Which of the following bones is part of the temporal region of the skull?

Temporal bone Signup and view all the answers

What does the sella turcica pertain to?

Sphenoid bone Signup and view all the answers

Which structure forms the nasal septum in conjunction with the vomer?

Ethmoid bone Signup and view all the answers

What is an accurate description of the mandible?

Only movable skull bone Signup and view all the answers

Which paranasal sinus is associated with the maxilla?

Maxillary sinus Signup and view all the answers

What distinguishes the hyoid bone from other bones in the body?

It has no direct bony attachment Signup and view all the answers

How many individual bones typically comprise the adult vertebral column?

26 Signup and view all the answers

What is the primary function of the axial skeleton?

Protecting vital organs and serving as a muscle attachment site Signup and view all the answers

Which components are included in the skeletal system?

Bones, cartilages, tendons, and ligaments Signup and view all the answers

How many bones are typically found in the appendicular skeleton of an adult?

126 Signup and view all the answers

What determines the characteristics of connective tissues in the skeletal system?

The composition of their extracellular matrix Signup and view all the answers

What type of protein is primarily found in the extracellular matrix of bone and cartilage to provide toughness?

Collagen Signup and view all the answers

What is the role of proteoglycans in the extracellular matrix of cartilage?

Making it smooth and resilient Signup and view all the answers

Which skeletal system function is least associated with the appendicular skeleton?

Blood cell production Signup and view all the answers

Which of the following tissues makes tendons and ligaments particularly tough?

Large amounts of collagen fibers Signup and view all the answers

What is the primary component of the bone extracellular matrix that provides flexible strength?

Collagen fibers Signup and view all the answers

Which type of bone is characterized as being longer than it is wide?

Long bone Signup and view all the answers

What is found at the ends of long bones and helps reduce friction?

Articular cartilage Signup and view all the answers

During growth, where does bone growth primarily occur in long bones?

Epiphyseal plate Signup and view all the answers

Which type of bone marrow is primarily found in the diaphysis of long bones in adults?

Yellow marrow Signup and view all the answers

What structure surrounds the outer surface of a bone?

Periosteum Signup and view all the answers

Which component of the bone is primarily responsible for weight-bearing strength?

Mineral component Signup and view all the answers

In newborns, where is the majority of blood-forming cells found?

Red marrow Signup and view all the answers

Study Notes

Skeletal System

The skeletal system consists of Bones, Cartilages, Tendons, and Ligaments.
Bones provide support, function, movement, storage, and blood cell production.
The axial skeleton is the central axis of the body, consisting of the head, neck, torso, and back bones.
The axial skeleton protects vital organs and serves as an attachment site for muscles.
The appendicular skeleton includes all bones of the upper and lower limbs, and the bones that attach each limb to the axial skeleton.
The appendicular skeleton contains 126 bones in an adult.
Extracellular matrix determines the characteristics of connective tissues like bones, cartilages, tendons, and ligaments.
The matrix is composed of collagen, ground substance, organic molecules, water, and minerals.
Collagen in tendons and ligaments provides strength, making them tough like ropes or cables.
Cartilage contains collagen and water-filled proteoglycans, making it tough and resilient.
Bone contains collagen and minerals, like calcium and phosphate.
Collagen lends flexibility while minerals provide weight-bearing strength to bone.
The mineral component in bone is mainly hydroxyapatite crystals.

Bone Shape Classifications

Long bones are longer than they are wide, examples include the upper and lower limb bones.
Short bones are approximately as wide as they are long, examples include wrist and ankle bones.
Flat bones are thin and flattened, examples include skull and sternum bones.
Irregular bones have unusual shapes, examples include vertebrae and facial bones.

Long Bone Structures

Diaphysis is the shaft of the bone, containing compact bone tissue on the outside.
Epiphysis are the ends of the bone, made of spongy bone tissue.
Articular cartilage covers the epiphyses, reducing friction.
Epiphyseal plate is located between the diaphysis and epiphysis, serving as the site of bone growth.
Medullary cavity is the center of the diaphysis, containing either red or yellow marrow.
Periosteum is the membrane that surrounds the outer surface of the bone.
Endosteum is the membrane that lines the medullary cavity.

Bone Marrow

Red marrow is responsible for blood cell formation.
Yellow marrow is primarily composed of fat.
In newborns, most bones contain red bone marrow.
In adults, red marrow in the diaphysis is replaced by yellow marrow.
In adults, most red marrow is found in flat bones and the long bones of the femur and humerus.

Compact Bone Tissue

Location: Outer part of the diaphysis of long bones and thinner surfaces of other bones.
Osteon: Structural unit of compact bone, containing lamella, lacunae, canaliculus, central canal, and osteocytes.
Lamella: Rings of bone matrix.
Lacunae: Spaces between lamella.
Canaliculus: Tiny canals that transport nutrients and remove waste.
Central canal: Center of the osteon, containing blood vessels.

Spongy Bone Tissue

Located at the epiphyses of long bones and the center of other bones.
Contains trabeculae, interconnecting rods with spaces filled with marrow.
Lacks osteons.

Bone Cells

Osteoblasts: Responsible for bone formation, repair, and remodeling.
Osteocytes: Maintain the bone matrix, formed from osteoblasts after bone matrix surrounds them.
Osteoclasts: Remove existing bone (bone reabsorption), contributing to bone repair and remodeling.

Bone Formation

Ossification: The process of bone formation by osteoblasts.
Intramembranous ossification: Bone formation within connective tissue membranes, primarily occurs in skull bones.
Endochondral ossification: Bone formation inside hyaline cartilage, occurs in long bones.

Intramembranous Ossification

Osteoblasts deposit bone matrix on the surface of connective tissue fibers, forming trabeculae.
Begins in ossification centers and trabeculae radiate outwards.
Usually, two or more centers in each flat skull bone, resulting in mature skull bones from fusion of these centers.
Trabeculae are constantly remodeled, expanding or replaced by compact bone.

Endochondral Ossification

Occurs within a cartilage model that is replaced by bone.
Primary ossification center forms first in the diaphysis of a long bone.
Secondary ossification center forms in the epiphysis.

Steps in Endochondral Ossification

Chondroblasts build a cartilage model and become chondrocytes.
Cartilage model calcifies.
Osteoblasts invade the calcified cartilage and form a primary ossification center in the diaphysis.
Secondary ossification centers form in the epiphysis.
The original cartilage model is almost completely ossified. Remaining cartilage becomes articular cartilage.

Bone Growth in Width

Appositional growth: Occurs by depositing new bone lamellae onto existing bone.
Osteoblasts deposit new bone matrix between the periosteum and existing bone matrix, increasing bone width or diameter.

Bone Growth in Length

Occurs in the epiphyseal plate, a major contributor to increased height.
Involves endochondral ossification.
Chondrocytes increase in number on the epiphyseal side of the epiphyseal plate.
Chondrocytes enlarge and die, causing calcification of the cartilage matrix.
Osteoclasts remove the enlarged cells and dying chondrocytes are replaced by osteoblasts.
Osteoblasts deposit new bone matrix on the calcified cartilage, forming bone on the diaphyseal side of the epiphyseal plate.

Bone Remodeling

Removal of existing bone (by osteoclasts) and deposition of new bone (by osteoblasts).
Occurs in all bones.
Responsible for changes in bone shape, repair, adjustment to stress, and calcium ion regulation.

Bone Repair

Bleeding and blood clot formation at the broken bone site.
Callus formation: A fibrous network between the two bone fragments.
Cartilage model formation followed by osteoblasts forming cancellous bone within the callus.
Remodeling of cancellous bone to form compact and cancellous bone.

Cranial Bones

Frontal bone: Anterior part of the cranium.
Parietal bones: Sides and roof of the cranium.
Occipital bone: Posterior portion and floor of the cranium.
Temporal bones: Inferior to parietal bones on each side of the cranium, forming the temporomandibular joint.
Sphenoid bone: Forms part of the cranium floor, lateral posterior portions of eye orbits, and lateral portions of the cranium anterior to temporal bones, contains the sella turcica.
Ethmoid bone: Forms the anterior portion of the cranium, including the medial surface of the eye orbit and roof of the nasal cavity, contains the nasal conchae.

Facial Bones

Maxillae: Form the upper jaw, anterior portion of the hard palate, part of the lateral walls of the nasal cavity, and floors of the eye orbits, contain the maxillary sinus.
Palatine bones: Form the posterior portion of the hard palate and the lateral wall of the nasal cavity.
Zygomatic bones: Cheek bones, also form the floor and lateral wall of each eye orbit.
Lacrimal bones: Medial surfaces of the eye orbits.
Nasal bones: Form the bridge of the nose.
Vomer: Midline of nasal cavity, forms the nasal septum with the ethmoid bone.
Inferior nasal conchae: Attached to lateral walls of the nasal cavity.
Mandible: Lower jawbone, the only movable skull bone.

Paranasal Sinuses

Cavities within several bones associated with the nasal cavity, opening into the nasal cavity.
Includes the frontal, ethmoid, sphenoid, and maxillary sinuses.

Hyoid Bone

Unpaired, U-shaped bone located in the neck.
Not part of the skull and has no direct bony attachment to other bones.
Provides attachment for tongue muscles and neck muscles that elevate the larynx.

Vertebral Column

Central axis of the skeleton, extending from the base of the skull to the end of the pelvis.
Usually consists of 26 bones in adults, grouped into five regions.
Has four major curvatures: cervical, thoracic, lumbar, and sacrococcygeal.
Cervical region curves anteriorly.

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Description

Explore the fundamental components of the skeletal system, including the differences between the axial and appendicular skeleton. Learn about the structure and function of bones, cartilages, tendons, and ligaments, as well as the role of the extracellular matrix in connective tissues.