chapter 15 ;The musculoskeletal system: support and movement Flashcards
What are the four types of cells found within bone tissue?
Osteogenic cells, osteoblasts, osteocytes, and osteoclasts.
What is the function of osteogenic cells?
- high mitotic activity;
- they differentiate and develop into osteoblasts.
- located: DEEP layers of the periosteum and endosteum
What role do osteoblasts play in bone tissue?
Osteoblasts are responsible for forming new bone; they synthesize and secrete the collagen matrix and calcium salts.
Where are osteoblasts found in bone tissue?
Osteoblasts are found in the growing portions of bone, such as the periosteum and endosteum.
Do osteoblasts divide?
No, osteoblasts do not divide.
What are osteocytes, and where are they located?
Osteocytes are the primary cell of mature bone, located in a space called a lacuna.
What is the main function of osteocytes?
Osteocytes maintain the mineral concentration of the bone matrix.
How do osteocytes communicate and receive nutrients?
They use long cytoplasmic processes to communicate with each other and receive nutrients.
Do osteocytes have mitotic activity?
No, like osteoblasts, osteocytes lack mitotic activity.
What is the function of osteoclasts?
Osteoclasts are responsible for bone resorption (breakdown).
Where are osteoclasts found in bone tissue?
Osteoclasts are found on bone surfaces.
What is unique about the origin of osteoclasts?
Osteoclasts are multinucleated and originate from monocytes and macrophages (types of white blood cells), not from osteogenic cells.
What is the microscopic structural unit of compact bone called?
An osteon, or Haversian system.
What is each osteon composed of?
oncentric rings of calcified matrix called lamellae (singular = lamella).
What runs down the center of each osteon?
The central canal, or Haversian canal.
What does the central (Haversian) canal contain?
Blood vessels, nerves, and lymphatic vessels.
What are the canals called that branch off at right angles to the central canal?
Perforating canals, also known as Volkmann’s canals.
Where are osteocytes located in compact bone?
Inside spaces called lacunae (singular = lacuna).
What is the nature of spongy bone?
Light, soft, and spongy.
What structural units make up spongy bone?
Trabeculae.
What function does the bone marrow in spongy bone have?
Produces red blood cells (RBCs) and white blood cells (WBCs).
What is the nature of compact bone?
Heavy, tough, and compact.
What structural units make up compact bone?
Osteons.
What function does the bone marrow in compact bone have?
Stores fat.
How are osteocytes housed in spongy bone compared to compact bone?
Osteocytes in spongy bone are housed in lacunae but are not arranged in concentric circles.
What network structure do lacunae and osteocytes form in spongy bone?
A lattice-like network of matrix spikes called trabeculae.
What is the purpose of the trabeculae in spongy bone?
They provide strength to the bone.
What balance do the spaces in the trabeculated network provide?
They make bones lighter to balance the dense, heavy compact bone, allowing muscles to move bones more easily.
What is contained within the spaces of the trabeculated network in spongy bone?
Red marrow, where hematopoiesis (the production of blood cells) occurs.
How does the trabeculae benefit the red marrow in spongy bone?
The trabeculae protect the red marrow.
What are the three main parts of a long bone?
Diaphysis, Metaphysis, Epiphysis
What is the diaphysis of a long bone?
The tubular shaft that runs between the ends of the bone.
What is the medullary cavity and where is it located?
The hollow region within the diaphysis, filled with yellow marrow.
What is the composition of the walls of the diaphysis?
Dense and hard compact bone.
What is the epiphysis of a long bone?
The wider section at the ends of the bone, filled with spongy bone.
What fills the spaces within the spongy bone in the epiphysis?
Red marrow.
What is the metaphysis in a long bone?
The region that connects the epiphysis and diaphysis and contains the epiphyseal plate (hyaline cartilage).
What happens to the epiphyseal plate after early adulthood (~18–21 years)?
The hyaline cartilage is replaced by osseous tissue, and the epiphyseal plate becomes an epiphyseal line.
What are the two bone linings and their functions?
Endosteum: Inner lining, where bone growth, repair, and remodeling occur.
Periosteum: Outer fibrous membrane that contains blood vessels, nerves, and lymphatic vessels to nourish compact bone.
What is the function of tendons and ligaments?
Tendons: Attach muscles to bones.
Ligaments: Attach bones to bones.
What is articular cartilage and where is it found?
A thin layer of cartilage that covers the epiphyses to reduce friction and act as a shock absorber
Which bones are formed through intramembranous ossification?
The flat bones of the face, most cranial bones, and the clavicles (collarbones).
What is the first step of intramembranous ossification?
Mesenchymal cells group into clusters, and ossification centers form.
What happens to osteoblasts during intramembranous ossification?
Secreted osteoid traps osteoblasts, which then become osteocytes
What structures form after osteoid secretion in intramembranous ossification?
The trabecular matrix and periosteum form.
What is endochondral ossification?
it is the process by which bone develops by replacing hyaline cartilage, which serves as a template to be fully replaced by new bone.
Where does compact bone develop in relation to trabecular bone?
Compact bone develops superficial to the trabecular bone.
How does endochondral ossification differ from intramembranous ossification in terms of time?
Endochondral ossification takes much longer than intramembranous ossification.
Which bones form through endochondral ossification?
Bones at the base of the skull and long bones.
What is the first step of endochondral ossification?
Mesenchymal cells differentiate into chondrocytes
What happens after chondrocytes form in endochondral ossification?
The cartilage model of the future bony skeleton and the perichondrium form.
What occurs when capillaries penetrate the cartilage?
The perichondrium transforms into periosteum, the periosteal collar develops, and the primary ossification center forms.
What happens to cartilage and chondrocytes as the bone begins to develop?
Cartilage and chondrocytes continue to grow at the ends of the bone.
What forms after the primary ossification center?
Secondary ossification centers develop.
Where does cartilage remain after endochondral ossification is complete?
Cartilage remains at the epiphyseal (growth) plate and at the joint surface as articular cartilage.
What are muscles made up of?
Muscles are made up of muscle fascicles
What is each muscle fascicle made of?
Each muscle fascicle is made of muscle fibers, or muscle cells.
What is the relationship between a muscle fiber and a muscle cell?
One muscle fiber is equivalent to one muscle cell.
What is the sarcolemma?
The sarcolemma is the plasma membrane of a muscle cell.
What is the sarcoplasm?
The sarcoplasm is the cytoplasm of a muscle cell.
What is the sarcoplasmic reticulum (SR)?
The sarcoplasmic reticulum (SR) is the endoplasmic reticulum (ER) of a muscle cell.
What structures make up each muscle fiber?
Each muscle fiber is made up of myofibrils.
What are the protective layers around muscle tissue?
The protective layers are the epimysium, perimysium, and endomysium.
What are myofibrils made of?
Myofibrils are made up of myofilaments enclosed in the sarcoplasmic reticulum (SR).
What is the sarcoplasmic reticulum (SR)?
The SR is an internal membrane complex in muscle cells, similar to the smooth endoplasmic reticulum
What are terminal cisternae?
Terminal cisternae are blind sacs of the SR that serve as reservoirs for calcium ions.
What forms a triad in muscle cells?
A triad is formed by two terminal cisternae with a T-tubule in between.
What is the function of calcium pumps in the SR?
Calcium pumps in the SR import calcium ions.
What is the role of calcium release channels in the SR?
Calcium release channels release calcium ions into the sarcoplasm in response to an electrical signal.
What triggers the release of calcium from the SR?
An electrical signal traveling down the T-tubule triggers the release of calcium into the sarcoplasm.
What is the structural unit of a myofibril?
The sarcomere is the structural unit of a myofibril.
How are myofilaments arranged within a sarcomere?
Myofilaments are arranged in repeating units called sarcomeres.
What types of filaments are found in a sarcomere?
sarcomere contains overlapping thick (myosin) and thin (actin) filaments.
What defines the boundaries of a sarcomere?
The sarcomere is delineated at both ends by Z discs.
What role do Z discs play in a sarcomere?
Z discs are specialized proteins perpendicular to the myofilaments that act as anchors for thin filaments.
What are I-bands in a sarcomere?
I-bands are regions that contain only thin filaments (actin) and appear lighter.
What are A-bands in a sarcomere?
A-bands are regions that contain thick filaments (myosin) and overlap with thin filaments, appearing darker.
What are myofilaments?
Myofilaments are contractile proteins within myofibrils responsible for muscle contraction.
What are the two types of myofilaments?
The two types are thick filaments and thin filaments.
What are thick filaments composed of?
Thick filaments consist of bundles of myosin protein molecules.
In which direction do myosin heads point in thick filaments?
Myosin heads point toward the ends of the filament.
What are thin filaments primarily composed of?
Thin filaments are composed of bundles of actin protein molecules.
What structure does actin form in thin filaments?
Actin forms twisted strands of F-actin, with each F-actin strand made up of G-actin monomers.
What is the function of G-actin in thin filaments?
G-actin has a myosin binding site where myosin heads attach during contraction.
Which regulatory proteins are found in thin filaments?
The regulatory proteins tropomyosin and troponin are present in thin filaments.
