Da bones

membrane of bones

A glistening white, double-layered membrane called the periosteum (per˝e-os´te-um; peri = around, osteo = bone) covers the external surface of the entire bone except the joint surfaces. The outer fibrous layer of the periosteum is dense irregular connective tissue. The inner osteogenic layer next to the bone surface contains osteoprogenitor cells (primitive stem cells that give rise to most bone cells). It also has bone-destroying cells (osteoclasts) and bone-forming cells (osteoblasts). The periosteum is richly supplied with nerve fibers and blood vessels, which is why broken bones are painful and bleed profusely. Perforating fibers—bundles of collagen fibers that extend into the bone matrix A delicate connective tissue membrane called the endosteum (en-dos´te-um; "within the bone") covers internal bone surfaces (Figure 6.5). The endosteum covers the trabeculae of spongy bone and lines the canals that pass through the compact bone. The endosteum contains the same cell types as the inner layer of the periosteum.

what is the diaphysis of a long bone

A tubular diaphysis (di-af′ĭ-sis; dia = through, physis = growth), or shaft, forms the long axis of the bone. It is constructed of a relatively thick collar of compact bone that surrounds a central medullary cavity (med´u-lar-e; "middle"), or marrow cavity, that contains no bone tissue. Instead, the medullary cavity contains yellow marrow (fat) in adults and so is called the yellow marrow cavity. Between the marrow and the compact bone, there is often a thin layer of spongy bone.

how does cartilage grow?

Appositional growth. In appositional growth(growth accomplished by the addition of new layers onto those previously formed , cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue. Interstitial growth. In interstitial growth (in˝ter-stish´al), the lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within. Typically, cartilage growth ends during adolescence when the skeleton stops growing. Under certain conditions—during normal bone growth in youth and during old age, for example—cartilage can become calcified

what are the skeletal hyaline cartilages

Articular cartilages (artic = joint, point of connection), which cover the ends of most bones at movable joints Costal cartilages, which connect the ribs to the sternum (breastbone) Respiratory cartilages, which form the skeleton of the larynx (voice box) and reinforce other respiratory passageways Nasal cartilages, which support the external nose

are bones organs?

Because they contain different types of tissue, bones are organs.Although bone (osseous) tissue dominates bones, they also contain nervous tissue in their nerves, cartilage in their articular cartilages, dense connective tissue covering their external surface, and muscle and epithelial tissues in their blood vessels

Gross anatomy of bone

Every bone has a dense outer layer that looks smooth and solid to the naked eye. This external layer is compact bone (Figures 6.3, 6.4, and 6.5). Internal to this is spongy bone (also called trabecular bone, its the internal layer of skeletal bone), a honeycomb of small needle-like or flat pieces called trabeculae (trah-bek´u-le; "little beams"). In living bones the open spaces between trabeculae are filled with red or yellow bone marrow.

hematopoietic tissue in bones

Hematopoietic (blood-forming) tissue is also called red marrow.found in different locations in infants and adults. In infants, the medullary cavity of the diaphysis and all areas of spongy bone contain red bone marrow As a result, red marrow in adults is only found in the cavities between trabeculae of spongy bones in: The flat bones of the skull, as well as the sternum, ribs, clavicles, scapulae, hip bones, and vertebrae The heads of the femur (thigh bone) and humerus (long bone of the arm) Compared to long bones (femur and humerus), the red marrow found in the spongy bone of flat bones (such as the sternum) and in some irregular bones (such as the hip bone) is much more active in hematopoiesis

What are the 3 types of cartilage

Hyaline cartilages, which look like frosted glass when freshly exposed, provide support with flexibility and resilience. They are the most abundant skeletal cartilages. Their chondrocytes are spherical (Figure 4.11g), and the only fiber type in their matrix is fine collagen fibers (which are undetectable microscopically).

what are the different types of bones based upon shape

Long bones, as their name suggests, are considerably longer than they are wide (Figure 6.2a). A long bone has a shaft plus two ends, which are often expanded. All limb bones except the patella (kneecap) and the wrist and ankle bones are long bones.The three bones in each of your fingers are long bones, even though they are small. Short bones are roughly cube shaped. The bones of the wrist and ankle are examples (Figure 6.2d). Sesamoid bones (ses´ah-moid; "shaped like a sesame seed") are a special type of short bone that form in a tendon (for example, the patella).Some sesamoid bones act to alter the direction of pull of a tendon. Others reduce friction and modify pressure on tendons to reduce abrasion or tearing. Flat bones are thin, flattened, and usually a bit curved. The sternum (breastbone), scapulae (shoulder blades), ribs, and most cranial bones of the skull are flat bones Irregular bones have complicated shapes that fit none of the preceding classes. Examples include the vertebrae and the hip bones (Figure 6.2b).

what is interstital lamellae

Lying between intact osteons are incomplete lamellae called interstitial lamellae (in˝ter-stish´al) (Figure 6.9c, right). They either fill the gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling (discussed later). Circumferential lamellae, located just deep to the periosteum and just superficial to the endosteum, extend around the entire circumference of the diaphysis (Figure 6.9a) and effectively resist twisting of the long bone.

what runs through the core of osteon

Running through the core of each osteon is the central canal, or Haversian canal, containing small blood vessels and nerve fibers that serve the osteon's cells. Canals of a second type called perforating canals, or Volkmann's canals (folk´mahnz), lie at right angles to the long axis of the bone and connect the blood and nerve supply of the medullary cavity to the central canals (Figure 6.9a). Unlike the central canals of osteons, the perforating canals are not surrounded by concentric lamellae, but like all other internal bone cavities, these canals are lined with endosteum.

what are the cartialages

Skeletal cartilage -which is made of some variety of cartilage tissue sculpted to fit its body location and function. Cartilage consists primarily of water. very resilient— has the ability to spring back to its original shape after being compressed. Cartilage contains no nerves or blood vessels. surrounded by a layer of dense irregular connective tissue, the perichondrium "around the cartilage"). The perichondrium acts as reinforcement to resist outward expansion when the cartilage is compressed. The perichondrium contains blood vessels nourish the cartilage cells. The thickness limited by the distance nutrients can diffuse through the matrix. has 3 types with the same basic components—cells called chondrocytes, enclosed in small cavities (lacunae) within an extracellular matrix containing a jellylike ground substance and fibers.

what are the seven functions of bone

Support. Bones provide a framework that supports the body and cradles its soft organs. For example, bones of lower limbs act as pillars to support the body trunk when we stand, and the rib cage supports the thoracic wall. Protection. The fused bones of the skull protect the brain. The vertebrae surround the spinal cord, and the rib cage helps protect the vital organs of the thorax. Anchorage. Skeletal muscles, which attach to bones by tendons, use bones as levers to move the body and its parts. As a result, we can walk, grasp objects, and breathe. The design of joints determines the types of movement possible. Mineral storage. Bone is a reservoir for minerals, most importantly calcium and phosphate. The stored minerals are released into the bloodstream in their ionic form as needed for distribution to all parts of the body. Indeed, "deposits" and "withdrawals" of minerals to and from the bones go on almost continuously. Blood cell formation. Most blood cell formation, or hematopoiesis (hem˝ah-to-poy-e´sis), occurs in the red marrow of certain bones. Triglyceride (fat) storage. Fat, a source of energy for the body, is stored as yellow marrow in the cavities of long bones. Hormone production. Bones produce osteocalcin, a hormone that helps to regulate insulin secretion, glucose homeostasis, and energy expenditure

what are inorganic components of bones

The balance of bone tissue (65% by mass) consists of inorganic hydroxyapatites (hi-drok˝se-ap´ah-tītz), or mineral salts, largely calcium phosphates present as tiny, tightly packed, needle-like crystals in and around collagen fibers in the extracellular matrix. The crystals account for the most notable characteristic of bone—its exceptional hardness, which allows it to resist compression. Because of the mineral salts they contain, bones last long after death and provide an enduring "monument." In fact, skeletal remains many centuries old reveal the shapes and sizes of ancient peoples, the kinds of work they did, and many of the ailments they suffered, such as arthritis.

what is the epiphyses

The epiphyses (e-pif′ĭ-sēz; singular: epiphysis) are the bone ends (epi = upon). An outer shell of compact bone forms the epiphysis exterior and the interior contains spongy bone. thin layer of articular (hyaline) cartilage covers the joint surface of each epiphysis, cushioning the opposing bone ends during movement and absorbing stress. Between the diaphysis and each epiphysis of an adult long bone is an epiphyseal line, a remnant of the epiphyseal plate. The epiphyseal plate, commonly called the growth plate, is a disc of hyaline cartilage that grows during childhood to lengthen the bone. The flared portion of the bone where the diaphysis and epiphysis meet, whether it is the epiphyseal plate or line, is called the metaphysis (meta = between).

Bone markings

The external surface of a bone is rarely smooth and featureless. Instead, it has distinct bone markings that provide a wealth of information about how that bone and its attached muscles and ligaments work together Bone markings fit into three categories: (1) projections that are sites of muscle and ligament attachment, (2) surfaces that form joints, and (3) depressions and openings for blood vessels and nerves.

blood vessles and nerves of bone

Unlike cartilage, bones are well vascularized. The main vessels serving the diaphysis are a nutrient artery (Figure 6.5c) and a nutrient vein. Together these run through a hole in the wall of the diaphysis, the nutrient foramen nutrient artery supply the bone marrow and the spongy bone. Branches then extend outward to supply the compact bone. Several epiphyseal arteries and veins serve each epiphysis in the same way. Nerves accompany blood vessels through the nutrient foramen into the bone.

what is an osteon

a system of interconnecting canals in the microscopic structure of adult compact bone; unit of bone; also called Haversian system an osteon is a group of hollow tubes of bone matrix, one placed outside the next like the growth rings of a tree trunk. Each matrix tube is a lamella (lah-mel´ah; "little plate"), and for this reason compact bone is often called lamellar bone. Although all of the collagen fibers in a particular lamella run in a single direction, the collagen fibers in adjacent lamellae always run in different directions. This alternating pattern beautifully withstands torsional stresses—the adjacent lamellae reinforce one another to resist twisting

structure of a typical long bone

all long bones have the same general structure: a shaft, bone ends, and membranes except for some.

what are Osteoprogenitor cells

also called osteogenic cells, are mitotically active stem cells found in the membranous periosteum and endosteum. In growing bones they are flattened or squamous cells. When stimulated, these cells differentiate into osteoblasts, while others persist as osteoprogenitor cells.

what are osteoclasts

are giant multinucleate cells located at sites of bone resorption. They are derived from the same white blood cell lineage that gives rise to macrophages. When actively resorbing (breaking down) bone, the osteoclasts lie in a shallow depression they have carved out. They have a distinctive ruffled border that directly contacts the bone. The deep plasma membrane infoldings of the ruffled border tremendously increase the surface area for enzymatically degrading the bones and seal off that area from the surrounding matrix.

what are osteoblasts

bone-forming cells that secrete the bone matrix. Like their close relatives, the fibroblasts and chondroblasts, they are actively mitotic. The unmineralized bone matrix they secrete includes collagen (90% of bone protein) and calcium-binding proteins that make up the initial unmineralized bone, or osteoid. As described later, osteoblasts also play a role in matrix calcification. When actively depositing matrix, osteoblasts are cube shaped. When inactive, they resemble the flattened osteoprogenitor cells or may differentiate into bone lining cells. When the osteoblasts become completely surrounded by the matrix being secreted, they become osteocytes.

does bone contain organic or inorganic substances

both organic and inorganic. when two substances are present in proper proportions bone is extremely strong and durable without being brittle Its soft organic components—including bone cells and osteoid— allow it to resist tension (stretch). Its hard inorganic components—mineral salts—allow it to resist compression. Healthy bone is half as strong as steel in resisting compression and fully as strong as steel in resisting tension.

what are some key characteristics of cartilage compared to bone

cartialage- surrounded by perichondrium no blood vessels(only in perchondrium) chondrocytes in lucunae flexible extracellular matrix extracellular matrix made by chondroblasts appositional growth and interstitial growth bone- surrounded by periosteum blood vessels and verves throughout osteocytes in lacunae rigid extracellular matrix(due to inorganic calcium salts) extracellular matrix(organic part) made by osteoblasts appositional growth only

what are Elastic cartilages?

cartilage with abundant elastic fibers:more flexible than hyaline cartilage They are found in only two skeletal locations the external ear and the epiglottis (the flap that bends to cover the opening of the larynx each time we swallow).

The human skeleton is initially made up of what?

cartilages and fibrous membranes

what are the organic components of bone

cells (osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts) and osteoid (os´te-oid), the organic part of the matrix. Osteoid, makes up approximately one-third of the matrix, includes ground substance (p. 128) collagen fibers, both of which are secreted by osteoblasts. These organic substances, particularly collagen, contribute both to a bone's structure and to the flexibility and tensile strength that allow it to resist stretch and twisting. Bone's resilience is thought to come from sacrificial bonds in or between collagen molecules. These bonds stretch and break easily on impact, dissipating energy to prevent the force from rising to a fracture value. In the absence of continued or additional trauma, most of the sacrificial bonds re-form.

what are bone lining cells

flat cells found on bone surfaces where bone remodeling is not going on. Like osteocytes, they are thought to help maintain the matrix.

what are the three levels we consider of bone structure.

gross, microscopic, and chemical.

what do spider shaped osteocytes occupy

lacunae (lac = hollow; una = little) at the junctions of the lamellae. Hairlike canals called canaliculi (kan˝ah-lik´u-li) radiate from the lacunae, connecting them to each other and to the central canal. The manner in which canaliculi are formed is interesting. As bone forms, the osteoblasts maintain contact with one another and existing osteocytes by gap junctions (p. 68) in their tentacle-like extensions. The osteoblasts secrete bone matrix, and are trapped within it as it hardens, becoming osteocytes. This leaves a system of tiny canals—the canaliculi—filled with tissue fluid and containing the osteocyte extensions. The canaliculi tie all the osteocytes in a mature osteon together, allowing them to communicate and permitting nutrients and wastes to be relayed from one osteocyte to the next throughout the osteon. It's as if the osteocytes are holding hands and passing notes to each other. Although bone matrix is hard and impermeable to nutrients, the canaliculi and gap junctions allow bone cells to be well nourished.

what are osteocytes

mature bone cells that occupy spaces (lacunae) that conform to their shape. Osteocytes monitor and maintain the bone matrix. They also act as stress or strain "sensors" and respond to mechanical stimuli (bone loading, bone deformation, weightlessness). Osteocytes communicate this information to the cells responsible for bone remodeling (osteoblasts and osteoclasts) so that bone matrix can be made or degraded as mechanical stresses dictate. Osteocytes can also trigger bone remodeling to maintain calcium homeostasis as we will see shortly.

what are the 5 major cell types that populate bone tissue

osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts all of which except for osteoclasts originate from embryonic connective tissue cells. The presence of bone cells is what makes bone a dynamic living tisue because these cells continuously resorb (break down) and deposit bone in a process called remodeling.

what is the structure of short, irregular, and flat bones

share a simple pattern: They all consist of thin plates of spongy bone (diploë) covered by compact bone. The compact bone is covered outside and inside by connective tissue membranes, respectively the periosteum and endosteum. However, these bones are not cylindrical and so they have no shaft or expanded ends. They contain bone marrow (between their trabeculae), but no well-defined marrow cavity. Where they form movable joints with their neighbors, hyaline cartilage covers their surfaces.

what is the microscopic anatomy of spongy bone

spongy bone looks like a poorly organized, even haphazard, tissue (see Figures 6.4 and 6.5b). However, the trabeculae in spongy bone align precisely along lines of stress and help the bone resist stress. These tiny bone struts are as carefully positioned as the cables on a suspension bridge. Only a few cells thick, trabeculae contain irregularly arranged lamellae and osteocytes interconnected by canaliculi. No osteons are present. Nutrients reach the osteocytes of spongy bone by diffusing through the canaliculi from capillaries in the endosteum surrounding the trabeculae.

the human skeleton id divided into two groups which are?

the axial skeleton forms the long axis of the body includes the bones of the skull, vertebral column, and rib cage (shown in orange in Figure 6.1). Generally these bones protect, support, or carry other body parts. The appendicular skeleton, bones of the upper and lower limbs and the girdles (shoulder bones and hip bones) that attach the limbs to the axial skeleton (colored gold in Figure 6.1). Bones of the limbs help us move from place to place (locomotion) and manipulate our environment. . The unique shape of each bone fulfills a particular need Bones are classified by their shape as long, short, flat, or irregular

what are fibrocartilages

the cartilage most ressistant to compression and stretch. Forms vertebral discs and knee joint cartilages consist of roughly parallel rows of chondrocytes alternating with thick collagen fibers (Figure 4.11i). Fibrocartilages occur in sites that are subjected to both pressure and stretch, such as the padlike cartilages (menisci) of the knee and the discs between vertebrae