![Bone-inside](https://upload.wikimedia.org/wikipedia/commons/4/4a/Bone-inside.jpg)
A trabecula (plural trabeculae, from Latin for "small beam") is a small, often microscopic,
tissue element in the form of a small
beam
Beam may refer to:
Streams of particles or energy
*Light beam, or beam of light, a directional projection of light energy
**Laser beam
*Particle beam, a stream of charged or neutral particles
**Charged particle beam, a spatially localized grou ...
,
strut
A strut is a structural component commonly found in engineering, aeronautics, architecture and anatomy. Struts generally work by resisting longitudinal compression, but they may also serve in tension.
Human anatomy
Part of the functionality o ...
or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally has a mechanical function, and is usually composed of dense
collagen
Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
ous tissue (such as the
trabecula
A trabecula (plural trabeculae, from Latin for "small beam") is a small, often microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally ha ...
of the
spleen
The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes . ). It can be composed of other material such as muscle and bone. In the
heart
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...
,
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
s form
trabeculae carneae
The trabeculae carneae (columnae carneae, or meaty ridges) are rounded or irregular muscular columns which project from the inner surface of the right and left ventricle of the heart.Moore, K.L., & Agur, A.M. (2007). ''Essential Clinical Anatomy: ...
and
septomarginal trabeculae.
Cancellous bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and ...
is formed from groupings of trabeculated bone tissue.
In cross section, trabeculae of a
cancellous bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and ...
can look like
septa
The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...
, but in three dimensions they are topologically distinct, with trabeculae being roughly rod or pillar-shaped and septa being sheet-like.
When crossing fluid-filled spaces, trabeculae may offer the function of resisting tension (as in the
penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...
, see for example
trabeculae of corpora cavernosa and
trabeculae of corpus spongiosum) or providing a cell filter (as in the
trabecular meshwork of the eye
The trabecular meshwork is an area of tissue in the eye located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humor from the eye via the anterior chamber (the chamber on the front of the e ...
).
Multiple perforations in a septum may reduce it to a collection of trabeculae, as happens to the walls of some of the
pulmonary alveoli
A pulmonary alveolus (plural: alveoli, from Latin ''alveolus'', "little cavity"), also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where oxygen is exchanged for carbon dioxide. A ...
in
emphysema
Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alve ...
.
Structure
Trabecular bone, also called
cancellous
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
bone, is porous bone composed of trabeculated bone tissue. It can be found at the ends of long bones like the femur, where the bone is actually not solid but is full of holes connected by thin rods and plates of bone tissue.
Red bone marrow, where all the blood cells are made, fills the space between the trabecular pores. Even though trabecular bone contains a lot of holes, its spatial complexity contributes the maximal strength with minimum mass. It is noted that the form and structure of trabecular bone are organized to optimally resist loads imposed by functional activities, like jumping, running and squatting. And according to
Wolff's Law
Wolff's law, developed by the German anatomist and surgeon Julius Wolff (surgeon), Julius Wolff (1836–1902) in the 19th century, states that bone in a healthy animal will adapt to the loads under which it is placed. If loading on a particular ...
, proposed in 1892, the external shape and internal architecture of bone are determined by external stresses acting on it.
The internal structure of the trabecular bone firstly undergoes adaptive changes along stress direction and then the external shape of
cortical bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and ...
undergoes secondary changes. Finally bone structure becomes thicker and denser to resist external loading.
Because of the increased occurrence of total joint replacement and its impact on bone remodeling, understanding the stress-related and adaptive process of trabecular bone has become a central concern for bone physiologists. To understand the role of trabecular bone in age-related bone structure and in the design for bone-implant systems, it is important to study the mechanical properties of trabecular bone as a function of variables such as anatomic site, bone density, and age related issues. Mechanical factors including modulus, uniaxial strength, and fatigue properties are must be taken into account.
Typically, the porosity percent of trabecular bone is in the range 75–95% and the density ranges from 0.2 to 0.8 g/cm
3.
It is noted that the porosity can reduce the strength of the bone, but also reduce its weight. The porosity and the manner that porosity is structured affect the strength of material. Thus, the micro structure of trabecular bone is typically oriented and
''grain
'' of porosity is aligned in a direction at which mechanical stiffness and strength are greatest. Because of the microstructural directionality, the mechanical properties of trabecular bone are highly an-isotropic. The range of
young's modulus
Young's modulus E, the Young modulus, or the modulus of elasticity in tension or compression (i.e., negative tension), is a mechanical property that measures the tensile or compressive stiffness of a solid material when the force is applied leng ...
for trabecular bone is 800 to 14,000 MPa and the strength of failure is 1 to 100 MPa.
As mentioned above, the mechanical properties of trabecular bone are very sensitive to apparent density. The relationship between modulus of trabecular bone and its apparent density was demonstrated by Carter and Hayes in 1976. The resulting equation states:
where
represents the modulus of trabecular bone in any loading direction,
represents the apparent density, and
and
are constants depending on the architecture of tissue.
Using scanning electron microscopy, it was found that the variation in trabecular architecture with different anatomic sites lead to different modulus. To understand structure-anisotropy and material property relations, one must correlate the measured mechanical properties of anisotropic trabecular specimens with the stereological descriptions of their architecture.
The compressive strength of trabecular bone is also very important because it is believed that the inside failure of trabecular bone arise from compressive stress. On the stress-strain curves for both trabecular bone and cortical bone with different apparent density, there are three stages in stress-strain curve. The first is the linear region where individual trabecula bend and compress as the bulk tissue is compressed.
The second stage occurs after yielding, where trabecular bonds start to fracture, and the final stage is the stiffening stage. Typically, lower density trabecular areas offer more deformed staging before stiffening than higher density specimens.
In summary, trabecular bone is very compliant and heterogeneous. The heterogeneous character makes it difficult to summarize the general mechanical properties for trabecular bone. High porosity makes trabecular bone compliant and large variations in architecture leads to high heterogeneity. The modulus and strength vary inversely with porosity and are highly dependent on the porosity structure. The effects of aging and small cracking of trabecular bone on its mechanical properties are a source of further study.
Clinical significance
Studies have shown that once a human reaches adulthood, bone density steadily decreases with age, to which loss of trabecular bone mass is a partial contributor.
Loss of bone mass is defined by the World Health Organization as
osteopenia
Osteopenia, known as "low bone mass" or "low bone density", is a condition in which bone mineral density is low. Because their bones are weaker, people with osteopenia may have a higher risk of fractures, and some people may go on to develop osteop ...
if
bone mineral density (BMD) is one standard deviation below mean BMD in young adults, and is defined as
osteoporosis
Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone ...
if it is more than 2.5 standard deviations below the mean.
A low bone density greatly increases risk for
stress fracture
A stress fracture is a fatigue-induced bone fracture caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated injury from repeated submaximal loading, such as running or ...
, which can occur without warning. The resulting low-impact fractures from osteoporosis most commonly occur in the
upper femur, which consists of 25-50% trabecular bone depending on the region, in the
vertebrae
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
, which are about 90% trabecular, or in the
wrist
In human anatomy, the wrist is variously defined as (1) the Carpal bones, carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known ...
.
When trabecular bone volume decreases, its original plate-and-rod structure is disturbed; plate-like structures are converted to rod-like structures and pre-existing rod-like structures thin until they disconnect and resorb into the body.
Changes in trabecular bone are typically gender-specific, with the most notable differences in bone mass and trabecular microstructure occurring within the age range for menopause.
Trabeculae degradation over time causes a decrease in bone strength that is disproportionately large in comparison to volume of trabecular bone loss, leaving the remaining bone vulnerable to fracture.
With osteoporosis there are often also symptoms of
osteoarthritis
Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the w ...
, which occurs when
cartilage
Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...
in joints is under excessive stress and degrades over time, causing stiffness, pain, and loss of movement.
With osteoarthritis, the underlying bone plays a significant role in cartilage degradation. Thus any trabecular degradation can significantly affect stress distribution and adversely affect the cartilage in question.
Due to its strong effect on overall bone strength, there is currently strong speculation that analysis in patterns of trabeculae degradation may be useful in the near future in tracking the progression of osteoporosis.
Birds
The hollow design of bird bones is multifunctional. It establishes high
specific strength
The specific strength is a material's (or muscle's) strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio or strength-to-mass ratio. In fiber or textile applic ...
and supplements open airways to accommodate the
skeletal pneumaticity
Skeletal pneumaticity is the presence of air spaces within bones. It is generally produced during development by excavation of bone by pneumatic diverticula (air sacs) from an air-filled space, such as the lungs or nasal cavity. Pneumatization is h ...
common to many birds. The
specific strength
The specific strength is a material's (or muscle's) strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio or strength-to-mass ratio. In fiber or textile applic ...
and resistance to
buckling
In structural engineering, buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a gr ...
is optimized through a bone design that combines a thin, hard shell that encases a spongy core of trabeculae.
The
allometry
Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932.
Overview
Allom ...
of the trabeculae allows the skeleton to tolerate loads without significantly increasing the bone mass.
The
Red-Tailed Hawk
The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members with ...
optimizes its weight with a repeating pattern of V-shaped struts that give the bones the necessary lightweight and stiff characteristics. The inner network of trabeculae shifts mass away from the
neutral axis
The neutral axis is an axis in the cross section of a beam (a member resisting bending) or shaft along which there are no longitudinal stresses or strains. If the section is symmetric, isotropic and is not curved before a bend occurs, then the neu ...
, which ultimately increases the resistance to
buckling
In structural engineering, buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a gr ...
.
As in humans, the distribution of trabeculae in bird species is uneven and is dependent on load conditions. The bird with the highest
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
of trabeculae is the
kiwi
Kiwi most commonly refers to:
* Kiwi (bird), a flightless bird native to New Zealand
* Kiwi (nickname), a nickname for New Zealanders
* Kiwifruit, an edible berry
* Kiwi dollar or New Zealand dollar, a unit of currency
Kiwi or KIWI may also ref ...
, a flightless bird.
There is also uneven distribution of trabeculae within similar species such as the
great spotted woodpecker or
grey-headed woodpecker
The grey-headed woodpecker (''Picus canus''), also known as the grey-faced woodpecker, is a Eurasian member of the woodpecker family, Picidae. Along with the more commonly found European green woodpecker and the Iberian green woodpecker, it is o ...
. After examining a micro
CT scan of the woodpecker's forehead, temporomandibulum, and occiput it was determined that there is significantly more trabeculae in the forehead and occiput.
Besides the difference in distribution, the
aspect ratio of the individual struts was higher in woodpeckers than in other birds of similar size such as the
Eurasian Hoopoe
The Eurasian hoopoe (''Upupa epops'') is the most widespread species of the genus '' Upupa''. It is a distinctive cinnamon coloured bird with black and white wings, a tall erectile crest, a broad white band across a black tail, and a long narrow ...
or the
lark
Larks are passerine birds of the family Alaudidae. Larks have a cosmopolitan distribution with the largest number of species occurring in Africa. Only a single species, the horned lark, occurs in North America, and only Horsfield's bush lark occu ...
.
The woodpeckers’ trabeculae are more plate-like while the hawk and lark have rod-like structures networked through their bones. The decrease in strain on the woodpecker's brain has been attributed to the higher quantity of thicker plate-like struts packed more closely together than the hawk or hoopoe or the lark.
Conversely, the thinner rod-like structures would lead to greater deformation. A destructive mechanical test with 12 samples show the woodpecker's trabeculae design has an average ultimate strength of 6.38MPa, compared to the lark's 0.55MPa.
Woodpeckers' beaks have tiny struts supporting the shell of the beak, but to a lesser extent compared to the skull. As a result of fewer trabeculae in the beak, the beak has a higher stiffness (1.0 GPa) compared to the skull (0.31 GPa). While the beak absorbs some of the impact from pecking, most of the impact is transferred to the skull where more trabeculae are actively available to absorb the shock. The ultimate strength of woodpeckers' and larks' beaks are similar, inferring the beak has a lesser role in impact absorption.
One measured advantage of the woodpecker's beak is the slight overbite (upper beak is 1.6mm longer than lower beak) which offers a
bimodal distribution
In statistics, a multimodal distribution is a probability distribution with more than one mode. These appear as distinct peaks (local maxima) in the probability density function, as shown in Figures 1 and 2. Categorical, continuous, and dis ...
of force due to the asymmetric surface contact. The staggered timing of impact induces a lower strain on the trabeculae in the forehead, occiput, and beak.
Research
Helmet technology
A significant cause of injury and death in humans involves head injury. Science has looked to woodpeckers to improve
helmet
A helmet is a form of protective gear worn to protect the head. More specifically, a helmet complements the skull in protecting the human brain. Ceremonial or symbolic helmets (e.g., a policeman's helmet in the United Kingdom) without protect ...
technology. It is noted that woodpeckers' heads decelerate at approximately 1,000 times the force of gravity continuously over an average of 15 pecks.
It is estimated that the woodpecker drums its beak approximately 12,000 times per day. It is assumed that the woodpeckers suffer no brain damage at forces that grossly exceed human capacity.
Riddell, a manufacturer of helmets for the
United States Army
The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
and
American football
American football (referred to simply as football in the United States and Canada), also known as gridiron, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, the team with ...
, is developing helmets to mitigate the stress on the front of the brain in a design similar to some birds.
Black box
Improvements to the impact strength of aeronautical
black box
In science, computing, and engineering, a black box is a system which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings. Its implementation is "opaque" (black). The te ...
es are being designed based on the head of a woodpecker. Hard layers of
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
and
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...
mimic woodpeckers' beak and skull, an
elastomer
An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus and high failure strain compared with other materials. The term, a portmanteau of ''elastic p ...
ic component to uniformly disperse vibrations , and a porous structure made of
glass microsphere
Glass microspheres are microscopic spheres of glass manufactured for a wide variety of uses in research, medicine, consumer goods and various industries. Glass microspheres are usually between 1 and 1000 micrometers in diameter, although the sizes ...
s to dampen vibrations similar to the action of trabecular bone. The resultant structure survived a test up to 60,000 Gs.
Trabecular metal material
Created by
Zimmer Biomet
Zimmer Biomet is a publicly traded medical device company. It was founded in 1927 to produce aluminum splints. The firm is headquartered in Warsaw, Indiana, where it is part of the medical devices business cluster.
In 2001, Zimmer was spun off f ...
, Trabecular Metal material has been used clinically for 19 years for orthopedic applications such as implantations for the hip, knee, or shoulder as well as bone void fillers, osteonecrosis rods, and dental implants. It consists of an open-cell
metal foam
Regular foamed aluminium
A metal foam is a cellular structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The pores can be sealed (closed-cell foam) or interconnected (open-c ...
with up to 80%
porosity
Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
with an average each pore size of 440 micrometers. It offers low stiffness and a high coefficient of
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
(0.98) allowing implants to remain secure without sliding. The material is pure
tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is ...
;
chemically inert
In chemistry, the term chemically inert is used to describe a substance that is not chemically reactive. From a thermodynamic perspective, a substance is inert, or nonlabile, if it is thermodynamically unstable (positive standard Gibbs free en ...
,
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
-resistant, and biocompatible. The trabecular structure offers high compressive modulus and high
fatigue strength in order to withstand normal physiological stresses over long periods of time.
[Zimmer Biomet, Zimmer Inc. https://www.zimmerbiomet.com/en/products-and-solutions/specialties/hip/trabecular-metal-technology.html]
Trabecula in other organisms
The larger the animal, the higher the load forces on its bones. Trabecular bone increases stiffness by increasing the amount of bone per unit volume or by altering the geometry and arrangement of individual trabeculae as body size and bone loading increases. Trabecular bone scales
allometrically, reorganizing the bones’ internal structure to increase the ability of the
skeleton
A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...
to sustain loads experienced by the trabeculae. Furthermore, scaling of trabecular geometry can moderate trabecular strain. Load acts as a
stimulus
A stimulus is something that causes a physiological response. It may refer to:
*Stimulation
**Stimulus (physiology), something external that influences an activity
**Stimulus (psychology), a concept in behaviorism and perception
*Stimulus (economi ...
to the trabecular, changing its geometry so as to sustain or mitigate strain loads. By using finite element modelling, a study tested four different species under an equal apparent stress (σapp) to show that trabecular scaling in animals alters the strain within the trabecular. It was observed that the strain within trabeculae from each species varied with the geometry of the trabeculae. From a scale of tens of micrometers, which is approximately the size of
osteocyte
An osteocyte, an oblate shaped type of bone cell with dendritic processes, is the most commonly found cell in mature bone. It can live as long as the organism itself. The adult human body has about 42 billion of them. Osteocytes do not divide and ...
s, the figure below shows that thicker trabeculae exhibited less strain. The relative frequency distributions of element strain experienced by each species shows a higher
elastic moduli
An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is ...
of the trabeculae as the species size increases.
Additionally, trabeculae in larger animals are thicker, further apart, and less densely connected than those in smaller animals. Intra-trabecular
osteon
In osteology, the osteon or haversian system (; named for Clopton Havers) is the fundamental functional unit of much compact bone. Osteons are roughly cylindrical structures that are typically between 0.25 mm and 0.35 mm in diameter. Their ...
can commonly be found in thick trabeculae of larger animals, as well as thinner trabeculae of smaller animals such as
cheetah
The cheetah (''Acinonyx jubatus'') is a large cat native to Africa and central Iran. It is the fastest land animal, estimated to be capable of running at with the fastest reliably recorded speeds being , and as such has evolved specialized ...
and
lemur
Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are Strepsirrhini, wet-nosed primates of the Superfamily (biology), superfamily Lemuroidea (), divided into 8 Family (biology), families and consisting of 15 genera and around 100 exist ...
s. The
osteon
In osteology, the osteon or haversian system (; named for Clopton Havers) is the fundamental functional unit of much compact bone. Osteons are roughly cylindrical structures that are typically between 0.25 mm and 0.35 mm in diameter. Their ...
s play a role in the diffusion of nutrients and waste products of osteocytes by regulating the distance between
osteocyte
An osteocyte, an oblate shaped type of bone cell with dendritic processes, is the most commonly found cell in mature bone. It can live as long as the organism itself. The adult human body has about 42 billion of them. Osteocytes do not divide and ...
s and bone surface to approximately 230 μm.
Due to an increased reduction of blood oxygen saturation, animals with high metabolic demands tend to have a lower trabecular thickness (Tb.Th) because they require increased vascular
perfusion
Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue, usually referring to the delivery of blood to a capillary bed in tissue. Perfusion is measured as the rate at which blood is deliver ...
of trabeculae. The
vascularization
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splitting ...
by tunneling
osteon
In osteology, the osteon or haversian system (; named for Clopton Havers) is the fundamental functional unit of much compact bone. Osteons are roughly cylindrical structures that are typically between 0.25 mm and 0.35 mm in diameter. Their ...
s changes the trabecular geometry from solid to tube-like, increasing bending stiffness for individual trabeculae and sustaining blood supply to deep tissue osteocytes.
Bone volume fraction (BV/TV) was found to be relatively constant for the variety of animal sizes tested. Larger animals did not show a significantly larger mass per unit volume of trabecular bone. This may be due to an
adaptation
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...
which reduces the physiological cost of producing, maintaining, and moving tissue. However, BV/TV showed significant positive scaling in avian
femoral condyle
The lower extremity of femur (or distal extremity) is the lower end of the femur (thigh bone) in human and other animals, closer to the knee. It is larger than the upper extremity of femur, is somewhat cuboid in form, but its transverse diameter i ...
s. Larger birds present decreased flight habits due to avian BV/TV
allometry
Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932.
Overview
Allom ...
. The flightless kiwi, weighing only 1–2 kg, had the greatest BV/TV of the birds tested in the study. This shows that trabecular bone geometry is related to ‘prevailing mechanical conditions’, so the differences in trabecular geometry in the femoral head and condyle could be attributed to different loading environments of
coxofemoral and
femorotibial joints.
The
woodpecker
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
’s ability to resist repetitive head impact is correlated with its unique micro/nano-hierarchical
composite
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic materials
...
structures.
Microstructure
Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as metals, polymers ...
and
nanostructure
A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale.
In describing nanostructures, it is necessary to differentiate between the number of dimens ...
of the
woodpecker
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
’s
skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
consists of an uneven distribution of
spongy bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
, the organizational shape of individual trabeculae. This affects the
woodpecker's mechanical properties, allowing the
cranial bone
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
to withstand a high
ultimate strength
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
(σu). Compared to the
cranial bone
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
of the
lark
Larks are passerine birds of the family Alaudidae. Larks have a cosmopolitan distribution with the largest number of species occurring in Africa. Only a single species, the horned lark, occurs in North America, and only Horsfield's bush lark occu ...
, the
woodpecker
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
cranial bone
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
is denser and less spongy, having a more plate-like structure rather than the more rod-like structure observed in
lark
Larks are passerine birds of the family Alaudidae. Larks have a cosmopolitan distribution with the largest number of species occurring in Africa. Only a single species, the horned lark, occurs in North America, and only Horsfield's bush lark occu ...
s. Furthermore, the
woodpecker's cranial bone
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
is thicker and more individual trabeculae. Relative to the trabeculae in
lark
Larks are passerine birds of the family Alaudidae. Larks have a cosmopolitan distribution with the largest number of species occurring in Africa. Only a single species, the horned lark, occurs in North America, and only Horsfield's bush lark occu ...
, the
woodpecker
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
’s trabecular is more closely spaced and more plate-like.
9These properties result in higher
ultimate strength
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
in the
cranial bone
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
of the
woodpecker
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...
.
History
The diminutive form of Latin ''trabs'', means a beam or bar. In the 19th century, the neologism ''trabeculum'' (with an assumed plural of ''trabecula'') became popular, but is less etymologically correct. ''Trabeculum'' persists in some countries as a synonym for the
trabecular meshwork
The trabecular meshwork is an area of tissue in the eye located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humor from the eye via the anterior chamber (the chamber on the front of the e ...
of the
eye, but this can be considered poor usage on the grounds of both etymology and descriptive accuracy.
Other uses
For the skull development component, see
trabecular cartilage.
References
{{Bone and cartilage
Tissues (biology)