Key Takeaways

Key PointsLong bones room those that are much longer than they space wide.The end of the long bone is the epiphysis and the column is the diaphysis. When a human finishes farming these parts fuse together.The exterior of the level bone consists of a layer of connective tissue dubbed the periosteum.The interior component of the long bone is the medullary cavity with the inner main point of the bone cavity being written of marrow.Flat bones have large surfaces for protection or muscular attachment.Flat bones room composed of 2 thin great of compact bone the surround a layer of cancellous (spongy) bone. In one adult, many red blood cells are formed in the marrow in level bones.Key Termsendosteum: A thin vascular membrane of connective organization that lines the surface ar of the bone organization that creates the medullary cavity of lengthy bones.

You are watching: Spongy, porous, trabecular bone is called:

medullary cavity: The medullary cavity, additionally known together the marrow cavity, is the main cavity the bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored.diaphysis: The main shaft of any long bone.epiphyseal plate: A hyaline cartilage key in the metaphysis, located at each finish of a lengthy bone where growth occurs in children and adolescents.

Bone Tissue

Bones support and protect the body and also its organs. They also produce miscellaneous blood cells, store minerals, and administer support because that mobility in conjunction with muscle. Bone is do of bone tissue, a type of thick connective tissue.

Bone (osseous) organization is the structural and supportive connective organization of the human body that forms the rigid component of the skeletal that consist of the skeleton. Overall, the bones of the body are an organ consisted of of bone tissue, bone marrow, blood vessels, epithelium, and also nerves.

There room two species of bone tissue: cortical and also cancellous bone. Cortical bone is compact bone, when cancellous bone is trabecular and spongy bone.

Cortical bone forms the very hard exterior while cancellous bone filling the interior. The tissues are biologically identical yet differ in the plan of their microstructure.

Bone Cells

The following are the different types of bone cells:

Osteoblasts-involved in the creation and also mineralisation of boneOsteocytes and also osteoclasts: these are involved in the reabsorption of bone tissue. The mineralized matrix of bone tissue has actually an essential component—mainly made of collagen—and an inorganic component of bone mineral comprised of assorted salts.

Bone Types

There are different species of bone. This are:

Long bonesShort bonesFlat bonesSesamoid bonesIrregular bones

Long bone: A lengthy bone is much longer than the is wide. Expansion occurs through a lengthening the the diaphysis. Located in the center of the lengthy bone.


Long bones thrive primarily by elongation that the diaphysis (the central shaft), v an epiphysis at each end of the farming bone. The end of epiphyses room covered with hyaline cartilage (articular cartilage). At the cessation that growth, the epiphyses fuse come the diaphysis, thus obliterating the intermediary area recognized as the epiphyseal bowl or development plate. The lengthy bones in the body space as follows:

Legs: The femur, tibia, and also fibula.Arms: The humerus, radius, and ulna.The clavicles or collar bones.Metacarpals, metarsals, phalanges.

The external of the bone is composed of a great of connective tissue dubbed the periosteum. The external shell that the lengthy bone is compact bone, listed below which lies a deeper layer of cancellous bone (spongy bone), as displayed in the following figure. The interior component of the lengthy bone is dubbed the medullary cavity; the inner core of the bone cavity is composed of marrow.

Short Bones

Short bones are about as broad as they room long. These administer support with much less movement. Examples of quick bones include the carpal and tarsal skeletal of the wrist and also feet. Lock consist of a thin layer that cortical bone through cancellous interiorly.


Compact bone and also spongy bone: The hard outer class of bones is written of compact bone tissue, so-called because of its minimal gaps and also spaces. That is porosity is 5–30%. Within the internal of the bone is the trabecular bone tissue, an open up cell, porous network that is additionally called cancellous or spongy bone. 


Flat Bones

Flat skeletal are large bones that administer protection or muscle attachment. They room composed of two thin class of compact bone surrounding a layer of cancellous (spongy) bone.

These bones are expanded into broad, level plates, as in the cranium (skull), ilium (pelvis), sternum, rib cage, sacrum, and scapula. The level bones space named:

OccipitalParietalFrontalNasalLacrimalVomerScapulaOs coxæ (hip bone)SternumRibs

Sesamoid Bone

Sesamoid skeletal are smaller sized bones the are resolved in tendons to protect them. An instance is the patella (knee cap) situated in the patellar tendon. Other examples encompass the little bones of the metatarsals and the pisiform skeleton of the carpus.

Irregular Bone

The irregular skeletal are named for their nonuniform shape. Examples include the bones of the vertebrae. These commonly have a thin cortical great with an ext cancellous bone in your tissue.


Supply that Blood and Nerves come Bone

The blood and nerve supply to skeletal are lugged in Haversian canals that run along the lengthy axis the bones.


Learning Objectives

Describe the blood and nerve it is provided of bones


Key Takeaways

Key PointsHaversian canals generally run parallel to the surface and along the lengthy axis that the bone and also generally save on computer one or two capillaries and nerve fibers.Volkmann’s canals are networks that help with blood and nerve it is provided from the periosteum to the Haversian canal.The vascular supply of long bones relies on number of points of inflow.Except for a couple of with dual or no foramina (places in bone where capillaries enervate), 90% of lengthy bones have actually a single nutrient foramen in the middle third of the shaft.Young periosteum is an ext vascular and also its ship communicate much more freely v those of the shaft contrasted to adult periosteum.Key Termsperichondrium: A layer of thick irregular connective tissue that surrounds the cartilage of occurring bone.Volkmann’s canal: likewise known as perforating holes, these are microscopic structures found in the compact bone that carry tiny arteries transparent the bone.anastomose: joined or run together.Haversian canal: A hole channel in the facility of an osteon, running parallel come the length of a bone.

Blood is offered to mature compact bone v the Haversian canal. Haversian canals are formed when individual lamellae form concentric rings around larger longitudinal canals (approx. 50 µm in diameter) in ~ the bone tissue.

Haversian canals typically run parallel come the surface and also along the long axis that the bone. The canals and also the neighboring lamellae (8–15) are referred to as a Haversian mechanism or one osteon. A Haversian canal generally consists of one or 2 capillaries and also nerve fibers.

The Haversian canals likewise surround nerve cells throughout the bone and also communicate through osteocytes in lacunae (spaces in ~ the thick bone procession that contain the living bone cells) with canaliculi. This unique arrangement is conducive come the warehouse of mineral salt deposits that give bone tissue its strength.


Haversian canal: The Haversian canals surround blood vessels and nerve cells throughout the bone.


The vascular it is provided of long bones depends on several points of inflow, i m sorry feed facility sinusoidal networks within the bone. This in turn drain to various channels through every surfaces of the bone other than that covered by articular cartilage.


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Volkmann’s canals are networks that help with blood and nerve it is provided from the periosteum to the Haversian canal. One or two main diaphyseal nutrient arteries enter the column obliquely with one or 2 nutrient foramina leading to nutrient canals. Your sites the entry and angulation are almost continuous and characteristically directed far from the growing epiphysis.

Except because that a couple of with double or no foramina, 90% of lengthy bones have actually a solitary nutrient foramen in the middle third of the shaft. The nutrient arteries divide right into ascending and also descending branches in the medullary cavity. These technique the epiphysis dividing into smaller rami. Near the epiphysis, they anastomose through the metaphyseal and also epiphyseal arteries.

The blood supply of the immature skeleton is similar, but the epiphysis is a discrete vascular zone separated indigenous the metaphysis through the expansion plate. Epiphyseal and also metaphyseal arteries go into on both political parties of the expansion cartilage, with anastamoses between them being couple of or absent.

Growth cartilage obtain its blood supply from both resources and also from one anastamotic collar in the adjoining perichondrium. Young periosteum is much more vascular, has more metaphyseal branches, and its ship communicate much more freely v those of the obelisk than adult periosteum.


Microscopic Anatomy the Bone

The an easy microscopic unit the bone is an osteon, which can be arranged into woven bone or lamellar bone.


Learning Objectives

Classify woven bone and also lamellar bone


Key Takeaways

Key PointsWoven bone is uncovered on the growing ends of one immature skeleton or, in adults, in ~ the site of a heal fracture.Woven bone is characterized by the irregular organization of collagen fibers and is mechanically weak, yet forms quickly.Lamellar bone is much stronger than woven bone, and also is very organized in concentric sheets through a much reduced proportion that osteocytes to mineralized tissue.When the very same lamellar bone is loose arranged, it is described as trabecular bone. Trabecular bone it s okay its name because of the spongy pattern it screens on one x-ray.After a fracture, woven bone forms initially and also is gradually replaced by lamellar bone throughout a process known as bony substitution.Key Termsosteoblast: A mononucleate cabinet from i beg your pardon bone develops.osteocytes: A star-shaped form of bone cell that is uncovered in the cell of mature bone.lamellar bone: A bone v a regular, parallel alignment the collagen into sheets (lamellae) that is mechanically strong.woven bone: defined by one irregular company of collagen fibers, this bone is mechanically weak.

Bones are composed of bone matrix, which has both organic and inorganic components. Bone matrix is laid down by osteoblasts as collagen, additionally known together osteoid. Osteoid is hardened with not natural salts, such together calcium and phosphate, and also by the chemicals exit from the osteoblasts with a process known as mineralization.

The straightforward microscopic unit the bone is an osteon (or Haversian system). Osteons are about cylindrical frameworks that have the right to measure several millimeters long and also around 0.2 mm in diameter.

Each osteon is composed of a lamellae that compact bone tissue that surround a main canal (Haversian canal). The Haversian canal consists of the bone’s blood supplies. The boundary of one osteon is called the cement line. Osteons have the right to be arranged into woven bone or lamellar bone.


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Osteon: A photo taken through a microscopic lense that shows the anatomy the compact bone with a thorough view of one osteon.


Woven Bone



Woven bone is uncovered on the growing ends of an immature skeleton or, in adults, at the site of a heal fracture. Woven bone is defined by the irregular organization of collagen fibers and also is mechanically weak, yet forms quickly.

The criss-cross illustration of the fibrous procession is why it is referred to as woven. It has actually a high proportion of osteocytes to difficult inorganic salts the leads to its mechanical weakness.

Woven bone is replaced by lamellar bone during development. In contrast to woven bone, lamellar bone is very organized in concentric sheets through a much lower proportion that osteocytes to neighboring tissue. The continuous parallel alignment of collagen right into sheets, or, lamellae, reasons lamellar bone to be mechanically strong.

Lamellar Bone



Lamellar bone provides up the compact or cortical bone in the skeleton, such as the lengthy bones the the legs and also arms. In a cross-section, the fibers of lamellar bone have the right to be checked out to operation in opposite directions in alternative layers, much like in plywood, assisting in the bone’s capability to stand up to torsion forces.

When the very same lamellar bone is loose arranged, the is described as trabecular bone. Trabecular bone gets its name since of the spongy pattern it displays in an x-ray. The spaces within trabecular bone room filled with active bone marrow.

After a fracture, woven bone forms initially, however it is progressively replaced by lamellar bone throughout a process known together bony substitution.


Chemical composition of Bone

Acid-base imbalances, including metabolic acidosis and alkalosis, can produce severe, even life-threatening medical conditions.


Learning Objectives

Differentiate amongst the acid-base disorders


Key Takeaways

Key PointsMetabolic acidosis can produce, amongst other symptoms, chest pains, changed mental states, nausea, abdominal muscle pain, and also muscle weakness.Rapid, deep breathing during metabolic acidosis is an attempt to lower carbon dioxide levels and also return pH to normal.Extreme acidemia have the right to lead to coma, seizures, love arrhythmias, and also low blood pressure.Slowed breathing, which results in retaining much more CO2, is the primary an approach of reducing metabolic alkalosis.Chronic respiratory tract acidosis is a an outcome of COPD, weight problems hypoventilation syndrome, ALS, and also thoracic deformities.Respiratory alkalosis have the right to be led to by too much mechanical ventilation, psychiatric problems, stroke, medicine use, travel to high altitude regions, lung disease, fever, and pregnancy, amongst other factors.Key Termsmetabolic alkalosis: A metabolic problem in i beg your pardon the pH of organization is elevated past the normal selection ( 7.35 come 7.45 ). This is the an outcome of reduced hydrogen ion concentration, leading to increased bicarbonate concentration, or a direct result of enhanced bicarbonate concentration.respiratory acidosis: A medical problem in which diminished ventilation (hypoventilation) causes increased blood carbon dioxide concentration and decreased pH (a condition generally dubbed acidosis).metabolic acidosis: A problem that occurs when the human body produces too lot acid or when the kidneys room not removing enough acid indigenous the body.

Examples

Traveling to a high altitude can cause an acid-base imbalance due to decreased levels of oxygen in the atmosphere, and, therefore, in the blood. Come compensate because that this, the traveler begins to hyperventilate, trying come expel overabundance carbon dioxide and also bring pH ago to normal. However, if the traveler continues to be at high altitude, it may take numerous days for your pH to fully return to normal.


Acid-Base Disorders

Acid-base imbalance is one abnormality of the human body’s typical balance the acids and also bases that causes the plasma pH come deviate the end of normal variety (7.35 come 7.45). In the fetus, the normal variety differs based on which umbilical ship is sampled (umbilical vein pH is generally 7.25 come 7.45; umbilical artery pH is generally 7.18 to 7.38). Acid-base imbalances deserve to exist in varying levels the severity, some life-threatening.

An overfill of mountain is dubbed acidosis and also an overfill in bases is dubbed alkalosis. The process that reasons the imbalance is classified based on the etiology the the disturbance (respiratory or metabolic) and the direction of change in pH (acidosis or alkalosis).

Mixed disorders may feature an acidosis and also alkalosis excess at the same time that partly counteract each other, or there can be 2 different problems affecting the pH in the same direction. The phrase blended acidosis, because that example, describes metabolic acidosis in conjunction through respiratory acidosis.

Metabolic Acidosis

In medicine, metabolic acidosis is a condition that occurs when the body produces too lot acid or when the kidneys room not removing sufficient acid from the body. If unchecked, metabolic acidosis leader to acidemia, that is, blood pH is much less than 7.35 as result of increased production of hydrogen through the body, or due to the fact that of the body’s i can not qualify to kind bicarbonate (HCO3-) in the kidneys.

Acidosis refers to a low pH in tissue. Acidemia refers to a short pH in the blood. Symptom may incorporate chest pain, palpitations, headache, altered mental condition such as significant anxiety because of hypoxia, reduced visual acuity, nausea, vomiting, ab pain, transformed appetite (either loss of or increased) and weight loss (longer term), muscle weakness, and bone pains.

Rapid deep breaths increase the quantity of carbon dioxide exhaled, therefore lowering the serum carbon dioxide levels, leading to some degree of compensation. Overcompensation via respiratory tract alkalosis to form an alkalemia does not occur.

Neurological complications incorporate lethargy, stupor, coma, seizures. Cardiac complications encompass arrhythmias (ventricular tachycardia) and decreased solution to epinephrine; both bring about hypotension (low blood pressure).

Metabolic Alkalosis

Metabolic alkalosis is a metabolic condition in i beg your pardon the pH of organization is elevated beyond the normal variety (7.35 come 7.45). This is the an outcome of decreased hydrogen ion concentration, top to enhanced bicarbonate concentration, or as a direct result of increased bicarbonate concentrations. Alkalosis describes a high pH in tissue.

Alkalemia describes a high pH in the blood. The causes of metabolic alkalosis deserve to be divided into two categories, relying on urine chloride levels. Chloride-responsive causes result from the loss of hydrogen ions via vomiting or the kidneys. Vomiting outcomes in the lose of hydrochloric mountain (hydrogen and chloride ions) v the stomach contents.

The kidney compensate because that these losses by retaining salt in the collecting ducts in ~ the price of hydrogen ion (sparing sodium/potassium pumps to prevent additional loss that potassium), and leads come metabolic alkalosis. The overfill sodium rises extracellular volume and also the ns of hydrogen ion creates a metabolic alkalosis.

Later, the kidney respond through the aldosterone escape to excrete sodium and chloride in urine. Compensation for metabolic alkalosis occurs greatly in the lungs, which retain carbon dioxide (CO2) v slower breathing, or hypoventilation (respiratory compensation).

CO2 is then consumed in the direction of the development of the carbonic mountain intermediate, therefore decreasing pH. Renal compensation for metabolic alkalosis, less reliable than respiratory compensation, is composed of raised excretion that HCO3– (bicarbonate), together the filtered pack of HCO3– exceeds the capability of the renal tubule come reabsorb it.

Respiratory Acidosis

Respiratory acidosis is a medical problem in which diminished ventilation (hypoventilation) causes boost in blood carbon dioxide concentration and decreased pH (a problem generally referred to as acidosis). Carbon dioxide is produced constantly together the body’s cell respire, and also this CO2 will accumulate rapidly if the lungs carry out not adequately expel it with alveolar ventilation.

Acute respiratory acidosis occurs once an abrupt fail of ventilation occurs. This fail in ventilation might be led to by depression that the central respiratory center by cerebral disease or drugs, an inability to ventilate adequately due to neuromuscular disease (e.g., myasthenia gravis, amyotrophic lateral sclerosis, Guillain-Barré syndrome, muscular dystrophy), or airway obstructions related to asthma or chronic obstructive pulmonary condition (COPD) exacerbation.

Respiratory Alkalosis

Respiratory alkalosis is a medical condition in which raised respiration (hyperventilation) elevates the blood pH (a condition generally referred to as alkalosis). There room two types of respiratory alkalosis: chronic and acute.

Acute respiratory tract alkalosis wake up rapidly. Throughout acute respiratory alkalosis, the human may lose consciousness whereupon the rate of ventilation will resume come normal.

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Chronic respiratory alkalosis is a much more long-standing condition. Respiratory alkalosis might be created accidentally (iatrogenically) throughout excessive mechanical ventilation. Other reasons include: psychiatric causes, drug use, fever, and also pregnancy.