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What Lines The Medullary Cavity

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Bone Tissue and the Skeletal System

Bone Structure

OpenStaxCollege

Learning Objectives

By the end of this department, yous volition be able to:

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

Bone tissue (osseous tissue) differs greatly from other tissues in the body. Bone is hard and many of its functions depend on that characteristic hardness. Afterwards discussions in this affiliate will show that bone is besides dynamic in that its shape adjusts to accommodate stresses. This section will examine the gross anatomy of bone first and so motion on to its histology.

Gross Anatomy of Bone

The structure of a long bone allows for the best visualization of all of the parts of a bone ([link]). A long os has ii 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 yellow marrow. The walls of the diaphysis are composed of dense and difficult compact bone.

Anatomy 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 bone is chosen the epiphysis (plural = epiphyses), which is filled with spongy bone. Red 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 os. When the bone stops growing in early adulthood (approximately 18–21 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line.

The medullary cavity has a delicate bleary lining called the endosteum (finish- = "within"; oste- = "bone"), where bone growth, repair, and remodeling occur. The outer surface of the bone 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 os. Tendons and ligaments also adhere to basic at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints ([link]). In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts equally 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.

Apartment bones, like those of the cranium, consist of a layer of diploë (spongy bone), lined on either side past a layer of meaty os ([link]). 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 yet protected by the intact inner layer.

Anatomy of a Flat Bone

This cross-section of a apartment bone shows the spongy os (diploë) lined on either side past a layer of meaty 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 function and location in the body. [link] describes the os markings, which are illustrated in ([link]). There are three general classes of bone markings: (1) articulations, (2) projections, and (3) holes. As the proper name implies, an articulation is where two bone surfaces come together (articulus = "joint"). These surfaces tend to conform to one some other, such as i existence rounded and the other cupped, to facilitate the function of the articulation. A project is an area of a bone that projects higher up the surface of the os. These are the attachment points for tendons and ligaments. In 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 bone that allows blood vessels and nerves to enter the bone. As with the other markings, their size and shape reverberate the size of the vessels and fretfulness that penetrate the bone at these points.

Bone Markings
Marking Description Instance
Articulations Where two bones run across Genu articulation
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 tin 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
Canal Passage in bone Auditory canal
Fissure Slit through bone Auricular crevice
Foramen Hole through bone Foramen magnum in the occipital os
Meatus Opening into culvert External auditory meatus
Sinus Air-filled space in os Nasal sinus

Bone Features

The surface features of bones depend on their function, 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

Os contains a relatively minor 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 every bit information technology crystallizes, or calcifies, on the collagen fibers. The hydroxyapatite crystals requite bones their hardness and strength, while the collagen fibers give them flexibility so that they are not brittle.

Although bone cells etch a pocket-size amount of the bone volume, they are crucial to the function of bones. Four types of cells are establish inside bone tissue: osteoblasts, osteocytes, osteogenic cells, and osteoclasts ([link]).

Os Cells

Four types of cells are constitute within bone tissue. Osteogenic cells are undifferentiated and develop into osteoblasts. When osteoblasts get trapped within the calcified matrix, their structure and part changes, and they get 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 prison cell responsible for forming new os and is establish in the growing portions of bone, including the periosteum and endosteum. Osteoblasts, which do not divide, synthesize and secrete the collagen matrix and calcium salts. As the secreted matrix surrounding the osteoblast calcifies, the osteoblast get trapped within it; as a result, it changes in structure and becomes an osteocyte, the chief prison cell of mature os and the well-nigh common type of os cell. Each osteocyte is located in a space chosen a lacuna and is surrounded by os tissue. Osteocytes maintain the mineral concentration of the matrix via the secretion of enzymes. Like osteoblasts, osteocytes lack mitotic activeness. They can communicate with each other and receive nutrients via long cytoplasmic processes that extend through canaliculi (atypical = canaliculus), channels inside the bone matrix.

If osteoblasts and osteocytes are incapable of mitosis, then how are they replenished when old ones die? The answer lies in the properties of a third category of bone cells—the osteogenic prison cell. These osteogenic cells are undifferentiated with high mitotic activity and they are the merely os cells that carve up. Immature osteogenic cells are institute 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 cell responsible for bone resorption, or breakdown, is the osteoclast. They are establish on bone surfaces, are multinucleated, and originate from monocytes and macrophages, 2 types of white blood cells, not from osteogenic cells. Osteoclasts are continually breaking downwardly old bone while osteoblasts are continually forming new os. The ongoing balance betwixt osteoblasts and osteoclasts is responsible for the constant but subtle reshaping of bone. [link] reviews the bone cells, their functions, and locations.

Os Cells
Cell type Part Location
Osteogenic cells Develop into osteoblasts Deep layers of the periosteum and the marrow
Osteoblasts Bone germination 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 onetime, injured, or unneeded bone

Meaty and Spongy Os

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

Meaty Bone

Compact bone is the denser, stronger of the two types of bone tissue ([link]). It tin can be found nether the periosteum and in the diaphyses of long bones, where information technology provides back up 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 can clearly see the concentric lamellae and primal canals. LM × 40. (Micrograph provided by the Regents of Academy of Michigan Medical Schoolhouse © 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 system. Each osteon is equanimous of concentric rings of calcified matrix called lamellae (atypical = lamella). Running down the center of each osteon is the fundamental canal, or Haversian canal, which contains blood vessels, nerves, and lymphatic vessels. These vessels and nerves branch off at correct angles through a perforating canal, also known as Volkmann's canals, to extend to the periosteum and endosteum.

The osteocytes are located inside spaces chosen lacunae (atypical = lacuna), plant at the borders of next lamellae. Every bit described before, canaliculi connect with the canaliculi of other lacunae and somewhen with the key culvert. This system allows nutrients to be transported to the osteocytes and wastes to exist removed from them.

Spongy (Cancellous) Bone

Similar compact bone, spongy os, too known as cancellous bone, contains osteocytes housed in lacunae, simply they are non bundled in concentric circles. Instead, the lacunae and osteocytes are found in a lattice-like network of matrix spikes called trabeculae (singular = trabecula) ([link]). The trabeculae may appear to be a random network, but each trabecula forms along lines of stress to provide strength to the bone. The spaces of the trabeculated network provide balance to the dense and heavy compact bone by making bones lighter so that muscles can motility them more easily. In addition, the spaces in some spongy bones comprise red marrow, protected past the trabeculae, where hematopoiesis occurs.

Diagram of Spongy Bone

Spongy bone is equanimous of trabeculae that comprise the osteocytes. Ruby 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.

Aging and the…

Skeletal Organization: Paget's Illness
Paget's illness usually occurs in adults over age forty. Information technology is a disorder of the bone remodeling procedure that begins with overactive osteoclasts. This ways more bone is resorbed than is laid down. The osteoblasts try to recoup but the new os they lay downwardly is weak and brittle and therefore decumbent to fracture.

While some people with Paget's affliction have no symptoms, others experience pain, bone fractures, and os deformities ([link]). Basic of the pelvis, skull, spine, and legs are the virtually commonly afflicted. When occurring in the skull, Paget'south disease tin cause headaches and hearing loss.

Paget'due south Disease

Normal leg basic are relatively straight, but those affected past Paget's illness 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 get overactive? The answer is yet unknown, just hereditary factors seem to play a role. Some scientists believe Paget'due south disease is due to an equally-however-unidentified virus.

Paget's disease is diagnosed via imaging studies and lab tests. 10-rays may prove 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 trunk. Areas of os resorption accept an affinity for the ion, so they will light up on the browse if the ions are absorbed. In improver, blood levels of an enzyme called alkali metal phosphatase are typically elevated in people with Paget's illness.

Bisphosphonates, drugs that decrease the activity of osteoclasts, are often used in the treatment of Paget's illness. Nonetheless, in a small percentage of cases, bisphosphonates themselves accept been linked to an increased risk of fractures considering the sometime os that is left subsequently bisphosphonates are administered becomes worn out and brittle. Nevertheless, most doctors feel that the benefits of bisphosphonates more than outweigh the gamble; the medical professional has to weigh the benefits and risks on a case-by-case ground. Bisphosphonate treatment can reduce the overall risk of deformities or fractures, which in plough reduces the risk of surgical repair and its associated risks and complications.

Claret and Nerve Supply

The spongy bone and medullary cavity receive nourishment from arteries that laissez passer through the compact bone. The arteries enter through the nutrient foramen (plural = foramina), small-scale openings in the diaphysis ([link]). The osteocytes in spongy bone are nourished by blood vessels of the periosteum that penetrate spongy os and claret that circulates in the marrow cavities. As the blood passes through the marrow cavities, it is collected past veins, which then pass out of the bone through the foramina.

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

Diagram of Claret and Nerve Supply to Bone

Blood vessels and nerves enter the bone 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.


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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 compact bone. The epiphyses, which are wider sections at each terminate of a long bone, are filled with spongy bone and cerise 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 bone, except in regions covered with articular cartilage, is covered with a gristly membrane called the periosteum. Flat bones consist of two layers of compact bone surrounding a layer of spongy os. Bone markings depend on the role and location of basic. Articulations are places where ii basic run across. Projections stick out from the surface of the bone and provide attachment points for tendons and ligaments. Holes are openings or depressions in the basic.

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

Review Questions

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

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

C

The diaphysis contains ________.

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

B

The fibrous membrane roofing the outer surface of the os is the ________.

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

A

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

C

Which cells do not originate from osteogenic cells?

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

D

Which of the following are found in compact bone and cancellous bone?

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

C

Which of the following are only plant in cancellous bone?

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

C

The expanse of a bone where the nutrient foramen passes forms what kind of bone mark?

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

A

Disquisitional Thinking Questions

If the articular cartilage at the stop of one of your long bones were to degenerate, what symptoms practise you think you lot would feel? Why?

If the articular cartilage at the end of one of your long bones were to deteriorate, which is actually what happens in osteoarthritis, y'all would feel articulation pain at the end of that bone and limitation of motion at that joint considering in that location would be no cartilage to reduce friction between side by side bones and there would be no cartilage to human activity equally a stupor cushion.

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

The densely packed concentric rings of matrix in compact bone are ideal for resisting compressive forces, which is the function of compact bone. The open spaces of the trabeculated network of spongy bone permit spongy bone to back up 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 as a stupor absorber
articulation
where two bone surfaces see
canaliculi
(singular = canaliculus) channels within the os matrix that business firm i of an osteocyte's many cytoplasmic extensions that it uses to communicate and receive nutrients
primal culvert
longitudinal channel in the middle of each osteon; contains claret vessels, nerves, and lymphatic vessels; also known every bit the Haversian canal
compact bone
dumbo osseous tissue that can 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 ii the layers of compact bone found in flat bones
endosteum
frail membranous lining of a bone'southward medullary cavity
epiphyseal plate
(likewise, growth plate) sheet of hyaline cartilage in the metaphysis of an immature bone; replaced past os tissue as the organ grows in length
epiphysis
wide department at each end of a long os; filled with spongy os and red marrow
hole
opening or low in a bone
lacunae
(singular = lacuna) spaces in a bone that house an osteocyte
medullary cavity
hollow region of the diaphysis; filled with yellow marrow
nutrient foramen
minor opening in the middle of the external surface of the diaphysis, through which an avenue enters the bone to provide nourishment
osteoblast
jail cell responsible for forming new os
osteoclast
jail cell responsible for resorbing bone
osteocyte
principal cell in mature bone; responsible for maintaining the matrix
osteogenic cell
undifferentiated cell with loftier mitotic activity; the merely bone cells that split up; they differentiate and develop into osteoblasts
osteon
(also, Haversian system) bones structural unit of compact bone; fabricated of concentric layers of calcified matrix
perforating canal
(also, Volkmann's canal) channel that branches off from the central 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
project
bone markings where role of the surface sticks out higher up the residuum of the surface, where tendons and ligaments attach
spongy bone
(also, cancellous os) trabeculated osseous tissue that supports shifts in weight distribution
trabeculae
(singular = trabecula) spikes or sections of the lattice-similar matrix in spongy bone

What Lines The Medullary Cavity,

Source: http://pressbooks-dev.oer.hawaii.edu/anatomyandphysiology/chapter/bone-structure/

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