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What Structure Allows a Bone to Grow in Length?

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Os Tissue and the Skeletal System

Os Structure

Learning Objectives

By the end of this section, y'all volition exist able to:

  • Identify the anatomical features of a bone
  • Define and list examples of bone markings
  • Depict the histology of os tissue
  • Compare and contrast meaty and spongy bone
  • Identify the structures that etch compact and spongy bone
  • Describe how bones are nourished and innervated

Os tissue (osseous tissue) differs greatly from other tissues in the body. Bone is hard and many of its functions depend on that feature hardness. Afterward discussions in this chapter will show that os is likewise dynamic in that its shape adjusts to arrange stresses. This section will examine the gross anatomy of bone kickoff and and then move on to its histology.

Gross Anatomy of Bone

The construction of a long bone allows for the best visualization of all of the parts of a bone ((Figure)). A long bone has two parts: the diaphysis and the epiphysis. The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone. The hollow region in the diaphysis is chosen the medullary cavity, which is filled with yellowish marrow. The walls of the diaphysis are composed of dumbo and hard compact bone.

Beefcake of a Long Bone

A typical long bone shows the gross anatomical characteristics of bone.

This illustration depicts an anterior view of the right femur, or thigh bone. The inferior end that connects to the knee is at the bottom of the diagram and the superior end that connects to the hip is at the top of the diagram. The bottom end of the bone contains a smaller lateral bulge and a larger medial bulge. A blue articular cartilage covers the inner half of each bulge as well as the small trench that runs between the bulges. This area of the inferior end of the bone is labeled the distal epiphysis. Above the distal epiphysis is the metaphysis, where the bone tapers from the wide epiphysis into the relatively thin shaft. The entire length of the shaft is the diaphysis. The superior half of the femur is cut away to show its internal contents. The bone is covered with an outer translucent sheet called the periosteum. At the midpoint of the diaphysis, a nutrient artery travels through the periosteum and into the inner layers of the bone. The periosteum surrounds a white cylinder of solid bone labeled compact bone. The cavity at the center of the compact bone is called the medullary cavity. The inner layer of the compact bone that lines the medullary cavity is called the endosteum. Within the diaphysis, the medullary cavity contains a cylinder of yellow bone marrow that is penetrated by the nutrient artery. The superior end of the femur is also connected to the diaphysis by a metaphysis. In this upper metaphysis, the bone gradually widens between the diaphysis and the proximal epiphysis. The proximal epiphysis of the femur is roughly hexagonal in shape. However, the upper right side of the hexagon has a large, protruding knob. The femur connects and rotates within the hip socket at this knob. The knob is covered with a blue colored articular cartilage. The internal anatomy of the upper metaphysis and proximal epiphysis are revealed. The medullary cavity in these regions is filled with the mesh like spongy bone. Red bone marrow occupies the many cavities within the spongy bone. There is a clear, white line separating the spongy bone of the upper metaphysis with that of the proximal epiphysis. This line is labeled the epiphyseal line.

The wider section at each terminate of the os is called the epiphysis (plural = epiphyses), which is filled with spongy bone. Ruddy marrow fills the spaces in the spongy bone. Each epiphysis meets the diaphysis at the metaphysis, the narrow area that contains the epiphyseal plate (growth plate), a layer of hyaline (transparent) cartilage in a growing bone. When the bone stops growing in early adulthood (approximately xviii–21 years), the cartilage is replaced past osseous tissue and the epiphyseal plate becomes an epiphyseal line.

The medullary cavity has a delicate membranous lining chosen the endosteum (finish- = "inside"; oste- = "os"), where bone growth, repair, and remodeling occur. The outer surface of the os is covered with a fibrous membrane chosen the periosteum (peri– = "around" or "surrounding"). The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments too adhere to bones at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other basic to form joints ((Figure)). In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber.

Periosteum and Endosteum

The periosteum forms the outer surface of bone, and the endosteum lines the medullary cavity.

The top of this illustration shows an anterior view of the proximal end of the femur. The top image has two zoom in boxes. The left box is situated on the border between the diaphysis and the metaphysis. Its callout magnifies the periosteum on the right side of the femur. The view shows that the periosteum contains an outer fibrous layer composed of yellow fibers. The inner layer of the periosteum is called the cellular layer, which is composed of irregularly shaped cells. The cellular layer gradually shrinks in width as it transitions from the metaphysis to the diaphysis. A small blood vessel runs through both layers and enters the bone. The right zoom in box magnifies the endosteum on the left side of the bone. The box is situated just inferior to the border between the diaphysis and the metaphysic. It calls out the inner edge of the compact bone layer. The magnified view shows concentric circles of dark colored bone matrix. Between the circles are small cavities containing orange, diamond-shaped cells labeled osteocytes. The left edge of the bone matrix is lined with a single layer of flattened cells called the endosteum. There is a large cell, labeled an osteoclast, between two of the endosteum cells. The osteoclast is cutting a depression into the bony matrix under the endosteum. At another part of the endosteum, three smaller osteoblasts are secreting a blue substance that builds up the outermost layer of the bony matrix.

Flat basic, like those of the cranium, consist of a layer of diploë (spongy bone), lined on either side by a layer of compact os ((Effigy)). The two layers of compact bone and the interior spongy bone work together to protect the internal organs. If the outer layer of a cranial bone fractures, the encephalon is even so protected by the intact inner layer.

Beefcake of a Apartment Bone

This cross-section of a apartment os shows the spongy bone (diploë) lined on either side past a layer of compact bone.

This illustration shows a cross section of a cranial bone, constructed somewhat like a sandwich. The topmost and bottommost layers are the thin, translucent, periosteum. The upper and lower periosteum cover an upper and lower layer of compact bone, respectively. The compact bone is solid, with each layer occupying about one tenth of the thickness of the cranial bone. The majority of the cross section is occupied by the spongy bone, or diploe, sandwiched between the upper and lower compact bone. The spongy bone contains many crisscrossing threads of bone. Dark air spaces occur between the threads, giving the bone a porous appearance, much like that of a sponge or Swiss cheese.

Bone Markings

The surface features of bones vary considerably, depending on the part and location in the body. (Effigy) describes the bone markings, which are illustrated in ((Figure)). There are three general classes of bone markings: (ane) articulations, (2) projections, and (3) holes. As the name implies, an articulation is where two bone surfaces come together (articulus = "joint"). These surfaces tend to conform to i another, such as one existence rounded and the other cupped, to facilitate the part of the articulation. A projection is an area of a bone that projects above the surface of the bone. These are the attachment points for tendons and ligaments. In full general, their size and shape is an indication of the forces exerted through the zipper to the bone. A hole is an opening or groove in the os that allows blood vessels and nerves to enter the bone. As with the other markings, their size and shape reflect the size of the vessels and nerves that penetrate the os at these points.

Os Markings
Marking Description Instance
Articulations Where two bones meet Knee joint
Head Prominent rounded surface Head of femur
Facet Apartment surface Vertebrae
Condyle Rounded surface Occipital condyles
Projections Raised markings Spinous process of the vertebrae
Protuberance Protruding Chin
Procedure Prominence feature Transverse process of vertebra
Spine Sharp process Ischial spine
Tubercle Small, rounded procedure Tubercle of humerus
Tuberosity Crude surface Deltoid tuberosity
Line Slight, elongated ridge Temporal lines of the parietal basic
Crest Ridge Iliac crest
Holes Holes and depressions Foramen (holes through which blood vessels can pass through)
Fossa Elongated basin Mandibular fossa
Fovea Small pit Fovea capitis on the head of the femur
Sulcus Groove Sigmoid sulcus of the temporal bones
Culvert Passage in bone Auditory canal
Fissure Slit through bone Auricular fissure
Foramen Hole through os Foramen magnum in the occipital os
Meatus Opening into culvert External auditory meatus
Sinus Air-filled space in bone Nasal sinus

Bone Features

The surface features of bones depend on their part, location, attachment of ligaments and tendons, or the penetration of blood vessels and nerves.

This illustration contains three diagrams. The left diagram is titled examples of processes formed where tendons or ligaments attach. The image shows an anterior view of the femur and an anterior view of the humerus. For the femur, the distal epiphysis contains a smaller lateral bulge and a larger medial bulge. These are examples of condyles. The inner halves of the two condyles as well as the groove between them compose a facet. An oval-shaped ridge on the medial surface of the distal metaphysis is an example of a tubercle. On the proximal epiphysis of the femur, the large knob that attaches to the hip socket is an example of a head. The tip of the head contains a small depression, an example of a fovea called the fovea capitis. On the humerus, the distal epiphysis contains a central depression that is an example of a fossa. Two condyles are located on the right and left sides of the fossa. The diaphysis of the humerus contains a small ridge running up the shaft that is an example of a tuberosity. The proximal epiphysis of the humerus contains a lateral and a medial bulge that are both examples of tubercles. Finally, a narrow groove runs from the center of the proximal metaphysis in between the medial and lateral condyles. This is an example of a sulcus. The middle image is entitled elevations or depressions. It shows an anterior view of the hip bones. The hip bones are shaped like two wings that join at the bottom. The crest along the upper edge of each hip bones, at the tip of each

Bone Cells and Tissue

Bone contains a relatively modest number of cells entrenched in a matrix of collagen fibers that provide a surface for inorganic salt crystals to adhere. These table salt crystals form when calcium phosphate and calcium carbonate combine to create hydroxyapatite, which incorporates other inorganic salts like magnesium hydroxide, fluoride, and sulfate as it crystallizes, or calcifies, on the collagen fibers. The hydroxyapatite crystals requite bones their hardness and force, while the collagen fibers give them flexibility so that they are not brittle.

Although os cells etch a small corporeality of the os volume, they are crucial to the part of basic. 4 types of cells are found within bone tissue: osteoblasts, osteocytes, osteogenic cells, and osteoclasts ((Figure)).

Bone Cells

Iv types of cells are found within bone tissue. Osteogenic cells are undifferentiated and develop into osteoblasts. When osteoblasts get trapped within the calcified matrix, their structure and office changes, and they go osteocytes. Osteoclasts develop from monocytes and macrophages and differ in appearance from other bone cells.

The top of this diagram shows the cross section of a generic bone with three zoom in boxes. The first box is on the periosteum. The second box is on the middle of the compact bone layer. The third box is on the inner edge of the compact bone where it transitions into the spongy bone. The callout in the periosteum points to two images. In the first image, four osteoblast cells are sitting end to end on the periosteum. The osteoblasts are roughly square shaped, except for one of the cells which is developing small, finger like projections. The caption says,

The osteoblast is the os cell responsible for forming new bone and is found in the growing portions of os, including the periosteum and endosteum. Osteoblasts, which exercise not divide, synthesize and secrete the collagen matrix and calcium salts. As the secreted matrix surrounding the osteoblast calcifies, the osteoblast become trapped within it; as a outcome, information technology changes in structure and becomes an osteocyte, the primary prison cell of mature os and the most common blazon of bone cell. Each osteocyte is located in a space called a lacuna and is surrounded by bone tissue. Osteocytes maintain the mineral concentration of the matrix via the secretion of enzymes. Like osteoblasts, osteocytes lack mitotic activity. They can communicate with each other and receive nutrients via long cytoplasmic processes that extend through canaliculi (atypical = canaliculus), channels within the bone matrix.

If osteoblasts and osteocytes are incapable of mitosis, then how are they replenished when onetime ones die? The respond lies in the properties of a third category of os cells—the osteogenic cell. These osteogenic cells are undifferentiated with loftier mitotic action and they are the simply bone cells that divide. Immature osteogenic cells are plant in the deep layers of the periosteum and the marrow. They differentiate and develop into osteoblasts.

The dynamic nature of bone means that new tissue is constantly formed, and old, injured, or unnecessary bone is dissolved for repair or for calcium release. The prison cell responsible for bone resorption, or breakup, is the osteoclast. They are found on bone surfaces, are multinucleated, and originate from monocytes and macrophages, ii types of white blood cells, not from osteogenic cells. Osteoclasts are continually breaking down old bone while osteoblasts are continually forming new bone. The ongoing balance between osteoblasts and osteoclasts is responsible for the constant but subtle reshaping of bone. (Figure) reviews the os cells, their functions, and locations.

Bone Cells
Prison cell type Function Location
Osteogenic cells Develop into osteoblasts Deep layers of the periosteum and the marrow
Osteoblasts Os formation Growing portions of os, including periosteum and endosteum
Osteocytes Maintain mineral concentration of matrix Entrapped in matrix
Osteoclasts Os resorption Bone surfaces and at sites of sometime, injured, or unneeded bone

Meaty and Spongy Os

The differences between compact and spongy bone are all-time explored via their histology. Most bones incorporate meaty and spongy osseous tissue, but their distribution and concentration vary based on the bone's overall part. Compact bone is dumbo so that it tin withstand compressive forces, while spongy (cancellous) bone has open spaces and supports shifts in weight distribution.

Compact Bone

Meaty bone is the denser, stronger of the two types of bone tissue ((Figure)). It can be establish under the periosteum and in the diaphyses of long bones, where information technology provides support and protection.

Diagram of Compact Bone

(a) This cross-sectional view of compact bone shows the basic structural unit, the osteon. (b) In this micrograph of the osteon, you lot can clearly come across the concentric lamellae and key canals. LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

A generic long bone is shown at the top of this illustration. The bone is split in half lengthwise to show its internal anatomy. The outer gray covering of the bone is labeled the periosteum. Within the periosteum is a thin layer of compact bone. The compact bone surrounds a central cavity called the medullary cavity. The medullary cavity is filled with spongy bone at the two epiphyses. A callout box shows that the main image is zooming in on the compact bone on the left side of the bone. On the main image, the periosteum is being peeled back to show its two layers. The outer layer of the periosteum is the outer fibrous layer. This layer has a periosteal artery and a periosteal vein running along its outside edge. The inner layer of the periosteum is labeled the inner osteogenic layer. The compact bone lies to the right of the periosteum and occupies the majority of the main image. Two flat layers of compact bone line the inner surface of the ostegenic periosteum. These sheets of compact bone are called the circumferential lamellae. The majority of the compact bone has lamellae running perpendicular to that of the circumferential lamellae. These concentric lamellae are arranged in a series of concentric tubes. There are small cavities between the layers of concentric lamellae called lacunae. The centermost concentric lamella surrounds a hollow central canal. A blue vein, a red artery, a yellow nerve and a green lymph vessel run vertically through the central canal. A set of concentric lamellae, its associated lacunae and the vessels and nerves of the central canal are collectively called an osteon. The front edge of the diagram shows a longitudinal cross section of one of the osteons. The vessels and nerve are visible running through the center of the osteon throughout its length. In addition, blood vessels can run from the periosteum through the sides of the osteons and connect with the vessels of the central canal. The blood vessels travel through the sides of the osteons via a perforating canal. The open areas between neighboring osteons are also filled with compact bone. This

The microscopic structural unit of compact bone is called an osteon, or Haversian arrangement. Each osteon is composed of concentric rings of calcified matrix called lamellae (atypical = lamella). Running down the center of each osteon is the key canal, or Haversian canal, which contains claret vessels, nerves, and lymphatic vessels. These vessels and nerves branch off at right angles through a perforating canal, also known as Volkmann'south canals, to extend to the periosteum and endosteum.

The osteocytes are located within spaces called lacunae (singular = lacuna), found at the borders of adjacent lamellae. As described earlier, canaliculi connect with the canaliculi of other lacunae and somewhen with the cardinal canal. This system allows nutrients to be transported to the osteocytes and wastes to exist removed from them.

Spongy (Cancellous) Bone

Like compact bone, spongy os, also known as cancellous bone, contains osteocytes housed in lacunae, but they are not bundled in concentric circles. Instead, the lacunae and osteocytes are found in a lattice-like network of matrix spikes called trabeculae (singular = trabecula) ((Figure)). The trabeculae may appear to be a random network, but each trabecula forms along lines of stress to provide strength to the os. The spaces of the trabeculated network provide balance to the dense and heavy compact os by making bones lighter so that muscles can movement them more easily. In addition, the spaces in some spongy bones contain red marrow, protected by the trabeculae, where hematopoiesis occurs.

Diagram of Spongy Bone

Spongy bone is equanimous of trabeculae that contain the osteocytes. Red marrow fills the spaces in some bones.

This illustration shows the spongy bone within the proximal epiphysis of the femur in two successively magnified images. The lower-magnification image shows two layers of crisscrossing trabeculae. The surface of each is dotted with small black holes which are the openings of the canaliculi. One of the trabeculae is in a cross section to show its internal layers. The outermost covering of the lamellae is called the endosteum. This endosteum surrounds several layers of concentric lamellae. The higher-magnification image shows the cross section of the trabeculae more clearly. Three concentric lamellae are shown in this view, each possessing perpendicular black lines. These lines are the canaliculi and are oriented on the round lamellae similar to the spokes of a wheel. In between the lamellae are small cavities called lacunae which house cells called osteocytes. In addition, two large osteoclasts are seated on the outer edge of the outermost lamellae. The outermost lamellae are also surrounded by groups of small, white, osteoblasts.

Crumbling and the…

Skeletal System: Paget's Disease Paget's disease commonly occurs in adults over age 40. It is a disorder of the bone remodeling process that begins with overactive osteoclasts. This means more than bone is resorbed than is laid down. The osteoblasts attempt to compensate but the new bone they lay down is weak and brittle and therefore prone to fracture.

While some people with Paget'due south illness accept no symptoms, others experience pain, bone fractures, and bone deformities ((Figure)). Basic of the pelvis, skull, spine, and legs are the most commonly affected. When occurring in the skull, Paget's disease can cause headaches and hearing loss.

Paget's Disease

Normal leg bones are relatively straight, but those afflicted past Paget's disease are porous and curved.

This illustration shows the normal skeletal structure of the legs from an anterior view. The flesh of the legs and feet are outlined around the skeleton for reference. A second illustration shows the legs of someone with Paget's disease. The affected person's left femur is curved outward, causing the left leg to be bowed and shorter than the right leg.

What causes the osteoclasts to become overactive? The answer is still unknown, merely hereditary factors seem to play a role. Some scientists believe Paget's disease is due to an as-yet-unidentified virus.

Paget's disease is diagnosed via imaging studies and lab tests. Ten-rays may show os deformities or areas of bone resorption. Bone scans are too useful. In these studies, a dye containing a radioactive ion is injected into the body. Areas of os resorption have an affinity for the ion, and then they volition low-cal upward on the scan if the ions are absorbed. In addition, blood levels of an enzyme chosen alkaline phosphatase are typically elevated in people with Paget's disease.

Bisphosphonates, drugs that decrease the activity of osteoclasts, are oftentimes used in the treatment of Paget's affliction. Nevertheless, in a small percentage of cases, bisphosphonates themselves accept been linked to an increased run a risk of fractures because the old bone that is left later bisphosphonates are administered becomes worn out and breakable. Yet, virtually doctors feel that the benefits of bisphosphonates more than than outweigh the gamble; the medical professional has to weigh the benefits and risks on a case-past-instance basis. Bisphosphonate treatment can reduce the overall run a risk of deformities or fractures, which in turn reduces the chance of surgical repair and its associated risks and complications.

Blood and Nerve Supply

The spongy bone and medullary cavity receive nourishment from arteries that pass through the compact os. The arteries enter through the nutrient foramen (plural = foramina), pocket-sized openings in the diaphysis ((Figure)). The osteocytes in spongy bone are nourished past blood vessels of the periosteum that penetrate spongy bone and blood that circulates in the marrow cavities. As the blood passes through the marrow cavities, it is nerveless by veins, which so pass out of the bone through the foramina.

In addition to the claret vessels, nerves follow the same paths into the bone where they tend to concentrate in the more metabolically active regions of the bone. The nerves sense hurting, and it appears the fretfulness also play roles in regulating blood supplies and in bone growth, hence their concentrations in metabolically agile sites of the os.

Diagram of Blood and Nerve Supply to Bone

Blood vessels and nerves enter the os through the food foramen.

This illustration shows an anterior view if the right femur. The femur is split in half lengthwise to show its internal anatomy. The outer covering of the femur is labeled the periosteum. Within it is a thin layer of compact bone that surrounds a central cavity called the medullary or marrow cavity. This cavity is filled with spongy bone at both epiphyses. A nutrient artery and vein travels through the periosteum and compact bone at the center of the diaphysis. After entering the bone, the nutrient arteries and veins spread throughout the marrow cavity in both directions. Some of the arteries and veins in the marrow cavity also spread into the spongy bone within the distal and proximal epiphyses. However, additional blood vessels called the metaphyseal arteries and the metaphyseal veins enter into the metaphysis from outside of the bone.

Watch this video to see the microscopic features of a bone.

Chapter Review

A hollow medullary cavity filled with yellow marrow runs the length of the diaphysis of a long bone. The walls of the diaphysis are meaty bone. The epiphyses, which are wider sections at each cease of a long bone, are filled with spongy os and red marrow. The epiphyseal plate, a layer of hyaline cartilage, is replaced by osseous tissue equally the organ grows in length. The medullary cavity has a delicate membranous lining called the endosteum. The outer surface of os, except in regions covered with articular cartilage, is covered with a fibrous membrane called the periosteum. Flat bones consist of 2 layers of compact bone surrounding a layer of spongy bone. Bone markings depend on the function and location of bones. Articulations are places where ii bones see. Projections stick out from the surface of the os and provide zipper points for tendons and ligaments. Holes are openings or depressions in the bones.

Bone matrix consists of collagen fibers and organic footing substance, primarily hydroxyapatite formed from calcium salts. Osteogenic cells develop into osteoblasts. Osteoblasts are cells that make new bone. They become osteocytes, the cells of mature os, when they get trapped in the matrix. Osteoclasts engage in bone resorption. Compact os is dense and composed of osteons, while spongy bone is less dense and made up of trabeculae. Blood vessels and nerves enter the bone through the nutrient foramina to nourish and innervate bones.

Review Questions

Which of the following occurs in the spongy os of the epiphysis?

  1. bone growth
  2. os remodeling
  3. hematopoiesis
  4. shock absorption

The diaphysis contains ________.

  1. the metaphysis
  2. fatty stores
  3. spongy os
  4. compact bone

The fibrous membrane covering the outer surface of the bone is the ________.

  1. periosteum
  2. epiphysis
  3. endosteum
  4. diaphysis

Which of the following are incapable of undergoing mitosis?

  1. osteoblasts and osteoclasts
  2. osteocytes and osteoclasts
  3. osteoblasts and osteocytes
  4. osteogenic cells and osteoclasts

Which cells do not originate from osteogenic cells?

  1. osteoblasts
  2. osteoclasts
  3. osteocytes
  4. osteoprogenitor cells

Which of the following are plant in compact bone and cancellous os?

  1. Haversian systems
  2. Haversian canals
  3. lamellae
  4. lacunae

Which of the following are merely institute in cancellous os?

  1. canaliculi
  2. Volkmann's canals
  3. trabeculae
  4. calcium salts

The area of a bone where the nutrient foramen passes forms what kind of os marker?

  1. a hole
  2. a facet
  3. a culvert
  4. a fissure

Disquisitional Thinking Questions

If the articular cartilage at the end of one of your long basic were to degenerate, what symptoms practice you think you would experience? Why?

If the articular cartilage at the end of one of your long bones were to deteriorate, which is really what happens in osteoarthritis, you would experience joint pain at the end of that bone and limitation of motion at that joint because there would be no cartilage to reduce friction between adjacent basic and in that location would be no cartilage to act as a shock cushion.

In what ways is the structural makeup of meaty and spongy bone well suited to their respective functions?

The densely packed concentric rings of matrix in meaty bone are ideal for resisting compressive forces, which is the part of compact bone. The open up spaces of the trabeculated network of spongy bone allow spongy bone to support shifts in weight distribution, which is the function of spongy bone.

Glossary

articular cartilage
thin layer of cartilage covering an epiphysis; reduces friction and acts equally a stupor absorber
articulation
where two bone surfaces meet
canaliculi
(singular = canaliculus) channels within the os matrix that firm one of an osteocyte'southward many cytoplasmic extensions that information technology uses to communicate and receive nutrients
cardinal canal
longitudinal channel in the centre of each osteon; contains blood vessels, fretfulness, and lymphatic vessels; likewise known as the Haversian canal
compact os
dense osseous tissue that tin withstand compressive forces
diaphysis
tubular shaft that runs between the proximal and distal ends of a long bone
diploë
layer of spongy os, that is sandwiched between two the layers of compact bone found in flat bones
endosteum
delicate bleary lining of a bone's medullary cavity
epiphyseal plate
(likewise, growth plate) sheet of hyaline cartilage in the metaphysis of an young os; replaced past bone tissue as the organ grows in length
epiphysis
broad section at each end of a long bone; filled with spongy os and red marrow
hole
opening or depression in a bone
lacunae
(singular = lacuna) spaces in a bone that firm an osteocyte
medullary cavity
hollow region of the diaphysis; filled with xanthous marrow
nutrient foramen
pocket-sized opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment
osteoblast
cell responsible for forming new bone
osteoclast
cell responsible for resorbing bone
osteocyte
primary prison cell in mature os; responsible for maintaining the matrix
osteogenic prison cell
undifferentiated jail cell with high mitotic activity; the just os cells that separate; they differentiate and develop into osteoblasts
osteon
(also, Haversian system) bones structural unit of meaty bone; made of concentric layers of calcified matrix
perforating canal
(also, Volkmann's culvert) channel that branches off from the key culvert and houses vessels and nerves that extend to the periosteum and endosteum
periosteum
fibrous membrane covering the outer surface of bone and continuous with ligaments
projection
bone markings where function of the surface sticks out in a higher place the residuum of the surface, where tendons and ligaments attach
spongy bone
(also, cancellous bone) trabeculated osseous tissue that supports shifts in weight distribution
trabeculae
(singular = trabecula) spikes or sections of the lattice-like matrix in spongy os

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Source: https://opentextbc.ca/anatomyandphysiologyopenstax/chapter/bone-structure/

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