What is the smallest bone in the human body?
Stapes
The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone, and the smallest in the human body. It rests on the oval window, to which it is connected by an annular ligament. The stapes is described as having a base, resting on the oval window, as well as a head that articulates with the incus. These are connected by anterior and posterior limbs (). The stapes articulates with the incus through the incudostapedial joint. The stapes is the smallest bone in the human body, and measures roughly 3 x 2.5mm, greater along the head-base span.
Capitate bone
The capitate bone is found in the center of the carpal bone region, colloquially known as the wrist, which is at the distal end of the radius and ulna bones. It articulates with the third metacarpal bone (the middle finger) and forms the third carpometacarpal joint. The capitate bone is the largest of the carpal bones in the human hand. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones; a constricted portion or neck; and below this, the body.
The bone is also found in many other mammals, and is homologous with the "third distal carpal" of reptiles and amphibians.
Smallest organisms
"Mycoplasma genitalium", a parasitic bacterium which lives in the primate bladder, waste disposal organs, genital, and respiratory tracts, is thought to be the smallest known organism capable of independent growth and reproduction. With a size of approximately 200 to 300 nm, "M. genitalium" is an ultramicrobacterium, smaller than other small bacteria, including rickettsia and chlamydia. However, the vast majority of bacterial strains have not been studied, and the marine ultramicrobacteria "Sphingomonas" sp strain RB2256 is reported to have passed through a 220 nm ultrafilter. A complicating factor is nutrient-downsized bacteria, bacteria that become much smaller due to a lack of available nutrients.
"Nanoarchaeum equitans" is a species of tiny microbe 400 nm in diameter. It was discovered in 2002 in a hydrothermal vent off the coast of Iceland by Karl Stetter. A thermophile that grows in near-boiling temperatures, "Nanoarchaeum" appears to be an obligatory symbiont on the archaeon "Ignicoccus"; it must be in contact with the host organism to survive.
Human skeleton
The axial skeleton (80 bones) is formed by the vertebral column (32–34 bones; the number of the vertebrae differs from human to human as the lower 2 parts, sacral and coccygeal bone may vary in length), a part of the rib cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones).
Venae cavae
The inferior vena cava (or caudal vena cava in some animals) travels up alongside the abdominal aorta with blood from the lower part of the body. It is the largest vein in the human body.
Neuroanatomy of memory
The occipital lobe is the smallest of all four lobes in the human cerebral cortex and located in the rearmost part of the skull and considered to be part of the forebrain. The occipital lobe sits directly above the cerebellum and is situated posterior to the Parieto-occipital sulcus, or parieto-occipital sulcus. This lobe is known as the centre of the visual perception system, the main function of the occipital lobe is that of vision.
Hand
There are numerous sesamoid bones in the hand, small ossified nodes embedded in tendons; the exact number varies between people: whereas a pair of sesamoid bones are found at virtually all thumb metacarpophalangeal joints, sesamoid bones are also common at the interphalangeal joint of the thumb (72.9%) and at the metacarpophalangeal joints of the little finger (82.5%) and the index finger (48%). In rare cases, sesamoid bones have been found in all the metacarpophalangeal joints and all distal interphalangeal joints except that of the long finger.
Smallest organisms
The smallest member of the order Carnivora is the least weasel ("Mustela nivalis"), with an average body length of 114–260 mm (4.5-10.2 in). It weighs between 29.5 – 250 grams with females being lighter.
Skeleton
There are 206 bones in the adult human skeleton, although this number depends on whether the pelvic bones (the hip bones on each side) are counted as one or three bones on each side (ilium, ischium, and pubis), whether the coccyx or tail bone is counted as one or four separate bones, and does not count the variable wormian bones between skull sutures. Similarly, the sacrum is usually counted as a single bone, rather than five fused vertebrae. There is also a variable number of small sesamoid bones, commonly found in tendons. The patella or kneecap on each side is an example of a larger sesamoid bone. The patellae are counted in the total, as they are constant. The number of bones varies between individuals and with age – newborn babies have over 270 bones some of which fuse together. These bones are organized into a longitudinal axis, the axial skeleton, to which the appendicular skeleton is attached.
Microchromosome
In rare cases, microchromosomes have been observed in the karotypes of individual humans. A link has been suggested between microchromosome presence and certain genetic disorders like Down syndrome and fragile X syndrome. The smallest chromosome in humans is normally chromosome 21, which is 47 Mb.
Etruscan shrew
The Etruscan shrew ("Suncus etruscus"), also known as the Etruscan pygmy shrew or the white-toothed pygmy shrew, is the smallest known mammal by mass, weighing only about on average. (The bumblebee bat is regarded as the smallest mammal by skull size and body length.)
Siriraj Medical Museum
Understanding human anatomy is at the core of the study of medicine. This museum has a collection, established by Dr Edgar Davidson Congdon, of more than 2,000 organs available for anatomical education. The museum displays the anatomical structure of all the systems of the human body, ranging from conception to reproductive age. Different forms of multiple births can be found on display. The range of muscles in the human body, the smallest of which is the size of an eyelash and the biggest of which is the size of a leg can also be seen. On display is a masterful dissection of the whole-body nervous and arterial system by Dr Patai Sirikarun, the one and only exhibit of its kind in the world.
Smallest organisms
The vulnerable Kitti's hog-nosed bat ("Craseonycteris thonglongyai"), also known as the bumblebee bat, from Thailand and Myanmar is the smallest mammal, at in length and in weight.
Third metacarpal bone
The third metacarpal bone (metacarpal bone of the middle finger) is a little smaller than the second.
Homo sapiens
The body skeletons of even the earliest and most robustly built modern humans were less robust than those of Neanderthals (and from what little we know from Denisovans), having essentially modern proportions. Particularly regarding the long bones of the limbs, the distal bones (the radius/ulna and tibia/fibula) are nearly the same size or slightly shorter than the proximal bones (the humerus and femur). In ancient people, particularly Neanderthals, the distal bones were shorter, usually thought to be an adaptation to cold climate. The same adaptation can be found in some modern people living in the polar regions.
Bridgette Jordan
Bridgette Marie Jordan (born June 9, 1989) is the former smallest living woman according to Guinness World Records at 2 ft 3in (69 cm). She is also one of the shortest living siblings according to Guinness World Records was her younger brother Brad is 38 inches tall at 20 years old (in 2011). Bridgette and Brad were born with a rare genetic condition called Microcephalic osteodysplastic primordial dwarfism type II. Bridgette is still the smallest woman in the USA. She lives in Sandoval, Illinois, having attended college at Kaskaskia College. Her hobbies are dancing and cheerleading. She was on the cheer squad for Kaskaskia. She wears an infant size 2 shoe.
Smallest cardiac veins
The thebesian veins are named after the German anatomist Adam Christian Thebesius, who described them in a 1708 treatise called "Disputatio medica inauguralis de circulo sanguinis in corde".
Second metacarpal bone
The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, of all the metacarpal bones.
Karl Stetter
"Nanoarchaeum equitans", an archaeal microorganism containing the world's smallest known genome, was discovered by Stetter in 2002 in a hydrothermal vent off the coast of Iceland. This archaebacterium was described in the scientific journal "Nature" in May 2002.
Nasuia deltocephalinicola
Nasuia deltocephalinicola was recently discovered to have the smallest genome of all bacteria, with 112,091 nucleotides. For comparison, the human genome has 3.2 billion nucleotides. The second smallest genome, from bacteria "Tremblaya princeps", has 139,000 nucleotides. While "Nasuia deltocephalinicola" has the smallest number of nucleotides it has more protein-coding genes than some bacteria, with 137 protein-coding genes.
Integumentary system
The skin is the largest organ of the body. In humans, it accounts for about 12 to 15 percent of total body weight and covers 1.5-2m of surface area.
Smallest cardiac veins
The smallest cardiac veins (or Thebesian veins) are minute valveless veins in the walls of all four heart chambers. The veins are sometimes accurately referred to as vessels, but they are frequently confused with a distinct set of artery connections eponymously referred to as the "vessels of Wearn". In his 1928 publication, Wearn himself referred to the arterio-cameral connections (vessels of Wearn) as thebesian. However, Wearn's 1933 and 1941 publications emphatically described the thebesian veins as distinct from arterio-cameral vessels.
Triad (anatomy)
In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally. (This property holds because T tubules run perpendicular to the longitudinal axis of the muscle fiber.) In mammals, triads are typically located at the A-I junction; that is, the junction between the A and I bands of the sarcomere, which is the smallest unit of a muscle fiber.
Fifth metacarpal bone
The fifth metacarpal bone (metacarpal bone of the little finger or pinky finger) is the most medial and second-shortest of the metacarpal bones.
Achilles tendon rupture
The Achilles tendon is the strongest and thickest tendon in the body, connecting the gastrocnemius, soleus and plantaris to the calcaneus. It is approximately 15 centimeters (5.9 inches) long and begins near the middle portion of the calf. Contraction of the gastrosoleus plantar flexes the foot, enabling such activities as walking, jumping, and running. The Achilles tendon receives its blood supply from its musculotendinous junction with the triceps surae and its innervation from the sural nerve and to a lesser degree from the tibial nerve.
Skeleton
Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Bones have a variety of shapes with a complex internal and external structure they are also lightweight, yet strong and hard. One of the types of tissue that makes up bone tissue is mineralized tissue and this
gives it rigidity and a honeycomb-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum and periosteum, nerves, blood vessels and cartilage. There are 206 bones in the adult human body and 270 in an infant.
Ulnar nerve
In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest unprotected nerve in the human body (meaning unprotected by muscle or bone), so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.
Human musculoskeletal system
The skeletal system serves many important functions; it provides the shape and form for the body, support and protection, allows bodily movement, produces blood for the body, and stores minerals. The number of bones in the human skeletal system is a controversial topic. Humans are born with over 300 bones; however, many bones fuse together between birth and maturity. As a result, an average adult skeleton consists of 206 bones. The number of bones varies according to the method used to derive the count. While some consider certain structures to be a single bone with multiple parts, others may see it as a single part with multiple bones. There are five general classifications of bones. These are long bones, short bones, flat bones, irregular bones, and sesamoid bones. The human skeleton is composed of both fused and individual bones supported by ligaments, tendons, muscles and cartilage. It is a complex structure with two distinct divisions; the axial skeleton, which includes the vertebral column, and the appendicular skeleton.
Madge Bester
Madge Bester (26 April 1963 – 19 March 2018) was a former world's shortest living woman. From South Africa, in 1991 she measured 2 ft 1.5 in (65 cm) in height. Bester had osteogenesis imperfecta, which is characterized by brittle bones, and used a wheelchair.
Navicular bone
The navicular bone in humans is one of the tarsal bones, found in the foot. Its name derives from the human bone's resemblance to a small boat, caused by the strongly concave proximal articular surface. The term "navicular bone" or "hand navicular bone" was formerly used for the scaphoid bone, one of the carpal bones of the wrist.
Ethmoid bone
The ethmoid bone (; from Greek "ethmos", "sieve") is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that make up the orbit of the eye.
Osteon
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 several millimeters long and around 0.2 mm in diameter. They are present in many bones of most mammals and some bird, reptile, and amphibian species.
Axial skeleton
Flat bones house the brain and other vital organs. This article mainly deals with the axial skeletons of humans; however, it is important to understand the evolutionary lineage of the axial skeleton. The human axial skeleton consists of 80 different bones. It is the medial core of the body and connects the pelvis to the body, where the appendix skeleton attaches. As the skeleton grows older the bones get weaker with the exception of the skull. The skull remains strong to protect the brain from injury.
Appendicular skeleton
The appendicular skeleton of 126 bones and the axial skeleton of 80 bones together form the complete skeleton of 206 bones in the human body. Unlike the axial skeleton, the appendicular skeleton is unfused. This allows for a much greater range of motion.
Louse
The human body louse "Pediculus humanus humanus" has (2010) the smallest insect genome known. This louse can transmit certain diseases while the human head louse ("P. h. capitis"), to which it is closely related, cannot. With their simple life history and small genomes, the pair make ideal model organisms to study the molecular mechanisms behind the transmission of pathogens and vector competence.
Ilium (bone)
The ilium () (plural ilia) is the uppermost and largest part of the hip bone, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.
Accessory bone
The "os carpi centrale" (also briefly "os centrale") is, where present, located on the dorsal side of the wrist between the scaphoid, the trapezoid and capitate, radially to the deep fossa of the capitate. The bone is present in almost every human embryo of 17–49 mm length, but then usually fuses with the ulnar side of the scaphoid. Sometimes it fuses with the capitate or the trapezoid. The literature also refers to an "os centrale" at the palm of the carpus, but this existence is questioned.
Ossicles
The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss. The term "ossicle" literally means "tiny bone". Though the term may refer to any small bone throughout the body, it typically refers to the malleus, incus, and stapes (hammer, anvil, and stirrup) of the middle ear.
Lesser wing of sphenoid bone
The lesser wing is connected to the body by two roots, the upper thin and flat, the lower thick and triangular; between the two roots is the optic foramen, for the transmission of the optic nerve and ophthalmic artery.
Clavicle
The clavicle or collarbone is a long bone that serves as a strut between the shoulder blade and the sternum or breastbone. There are two clavicles, one on the left and one on the right. The clavicle is the only long bone in the body that lies horizontally. Together with the shoulder blade it makes up the shoulder girdle. It is a touchable bone and in people who have less fat in this region, the location of the bone is clearly visible, as it creates a bulge in the skin. It receives its name from the ("little key") because the bone rotates along its axis like a key when the shoulder is abducted. The clavicle is the most commonly fractured bone. It can easily be fractured due to impacts to the shoulder from the force of falling on outstretched arms or by a direct hit.
Moulage
Andreas Vesalius (1514-1564), a Flemish anatomist, was at first a "Galenist" at the University of Paris. When he moved to Italy and entered the University of Padua, he began dissecting human bodies. He studied many details of human anatomy and found that Galen made some anatomical mistakes. For example, Galen wrote that the sternum has seven segments, but Vesalius found it has three segments. Galen wrote that the bone of the arm is the longest bone in the human body, but Vesalius found that the bone of the thigh is actually the longest bone in human body. At age 25 Vesalius realized that the anatomical knowledge of Galen was derived from animal anatomy and therefore Galen had never dissected a human body.
Coffin bone
The coffin bone, also known as the pedal bone (U.S.), is the bottommost bone in the equine leg and is encased by the hoof capsule. Also known as the distal phalanx, third phalanx, or "P3". The coffin bone meets the short pastern bone or second phalanx at the coffin joint. The coffin bone is connected to the inner wall of the horse hoof by a structure called the laminar layer. The insensitive laminae coming in from the hoof wall connects to the sensitive laminae layer, containing the blood supply and nerves, which is attached to the coffin bone. The lamina is a critical structure for hoof health, therefore any injury to the hoof or its support system can in turn affect the coffin bone.
List of bones of the human skeleton
The pelvis (or hip bone) is made up of three regions that have fused to form two coxal bones. They are: ilium, ischium, and pubisThere are a total of 60 bones in the legs.
Fibula
The fibula or calf bone is a leg bone located on the lateral side of the tibia, with which it is connected above and below. It is the smaller of the two bones and in proportion to its length, the slenderest of all the long bones. Its upper extremity is small, placed toward the back of the head of the tibia, below the level of the knee joint, and excluded from the formation of this joint. Its lower extremity inclines a little forward, so as to be on a plane anterior to that of the upper end; it projects below the tibia, and forms the lateral part of the ankle-joint.
Human skeleton
The appendicular skeleton (126 bones) is formed by the pectoral girdles, the upper limbs, the pelvic girdle or pelvis, and the lower limbs. Their functions are to make locomotion possible and to protect the major organs of digestion, excretion and reproduction.
Common pheasant
As of 2005, it had the smallest known genome of all living amniotes, only 0.97 pg (970 million base pairs), roughly one-third of the human genome's size; however, the black-chinned hummingbird is now currently held to have the smallest.
P. K. Sethi
The Jaipur foot is made of rubber and wood and is probably the lowest cost prosthetic limb available in the world. The International Red Cross Committee has used it extensively in Afghanistan and other places to help amputees. Several injured soldiers in the Kargil war were benefited due to the Jaipur foot. Sethi was recognized by the Guinness Book of World Records for helping a large number of amputees in obtaining mobility again. The Indian dancer and actor Sudha Chandran was one of his patients.
Microvessel
Microvessels are the smallest blood vessels in a body, including those responsible for microcirculation. They make up the microvasculature that distributes blood within tissues. Common examples of microvessels include:
Patu digua
By some accounts it is the smallest spider in the world, as males reach a body size of only about 0.37 mm - roughly one fifth the size of the head of a pin. However, there are other spider species of similar size where only the female is known; and male spiders are generally smaller.
List of bones of the human skeleton
The human skeleton of an adult consists of 206-208 bones. It is composed of 270 bones at birth, but later decreases to 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. Many small supernumerary bones, such as some sesamoid bones, are not included in this count.
Bone
In the human body at birth, there are over 270 bones, but many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small sesamoid bones. The largest bone in the body is the femur or thigh-bone, and the smallest is the stapes in the middle ear.
Nanobe
A nanobe is a tiny filamental structure first found in some rocks and sediments. Some scientists hypothesize that nanobes are the smallest form of life, 1/10 the size of the smallest known bacteria.
Fibula
The word "fibula" can be dated back to c. 1670 to describe a clasp or brooch – see fibula (brooch) – and was first used in English for the smaller bone in the lower leg c. 1706. It derives from Latin "fībula," also meaning a clasp or brooch. The bone was so called because it resembles a clasp like a modern safety pin.
Lunate bone
The lunate bone (semilunar bone) is a carpal bone in the human hand. It is distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row carpal bones, which lie between the ulna and radius and the hand. The lunate carpal bone is situated between the lateral scaphoid bone and medial triquetral bone.
Phalanx bone
The phalanges are the bones that make up the fingers of the hand and the toes of the foot. There are 56 phalanges in the human body, with fourteen on each hand and foot. Three phalanges are present on each finger and toe, with the exception of the thumb and large toe, which possess only two. The middle and far phalanges of the fourth and fifth toes are often fused together (symphalangism). The phalanges of the hand are commonly known as the finger bones. The phalanges of the foot differ from the hand in that they are often shorter and more compressed, especially in the proximal phalanges, those closest to the body.
Chandra Bahadur Dangi
Dangi was born on 30 November 1939. It is unknown what medical condition limited his growth. He lived in a remote village, Reemkholi, approximately away from Kathmandu, Nepal's capital. Before being recognised by the Guinness World Records as the world's shortest man in 2012, he had never left his home village. After being awarded the title, he said he had always wished to travel to all parts of his country and the world. He stated that being the shortest man in the world and a citizen of Nepal, he wanted to use his status to popularise his country.
Bone marrow
Bone marrow is a semi-solid tissue which may be found within the spongy or cancellous portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production or hematopoiesis. It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells. In adult humans, bone marrow is primarily located in the ribs, vertebrae, sternum, and bones of the pelvis. On average, bone marrow constitutes 4% of the total body mass of humans; in an adult having 65 kilograms of mass (143 lb), bone marrow typically accounts for approximately .
Human skin
In terms of surface area, the skin is the second largest organ in the human body (the inside of the small intestine is 15 to 20 times larger). For the average adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.). The thickness of the skin varies considerably over all parts of the body, and between men and women and the young and the old. An example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female. The average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings. The average human skin cell is about 30 micrometers in diameter, but there are variants. A skin cell usually ranges from 25-40 micrometers (squared), depending on a variety of factors.
Tibia
The tibia (plural tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia), and it connects the knee with the ankle bones. The tibia is found on the medial side of the leg next to the fibula and closer to the median plane or centre-line. The tibia is connected to the fibula by the interosseous membrane of the leg, forming a type of fibrous joint called a syndesmosis with very little movement. The tibia is named for the flute "tibia". It is the second largest bone in the human body next to the femur. The leg bones are the strongest long bones as they support the rest of the body.
Tantulocarida
Members of this subclass are minute – less than in length and have a dramatic reduction in body form compared to other crustaceans, with an unsegmented, sac-like thorax and a much reduced abdomen. One tantulocarid species, "Tantulacus dieteri", is the world's smallest arthropod, with a total body length of only .
Smallest organisms
The smallest crocodilian is the Cuvier's dwarf caiman ("Paleosuchus palpebrosus") from northern and central South America. It reaches up to in length.
Smallest organisms
The one of world's smallest fish based on the minimum size at maturity is "Paedocypris progenetica" from Indonesia, with mature females measuring as little as in standard length. This fish, a member of the carp family, has a translucent body and a head unprotected by a skeleton.
Fifth metatarsal bone
The fifth metatarsal bone is a long bone in the foot, and is palpable along the distal outer edges of the feet. It is the second smallest of the five metatarsal bones. The fifth metatarsal is analogous to the fifth metacarpal bone in the hand
Survivin
Survivin is distinguished from other IAP family members in that it has only one BIR domain. The mice and human BIR domain of survivin are very similar structurally except for two differences that may affect function variability. The human survivin also contains an elongated C-terminal helix comprising 42 amino acids. Survivin is 16.5 kDa large and is the smallest member of the IAP family.
X-ray crystallography has shown two molecules of human surviving coming together to form a bowtie-shape dimer through a hydrophobic interface. This interface includes N-terminal residues 6-10 just before the BIR domain region and the 10 residue region connecting the BIR domain to the C-terminal helix. The structural integrity of the determined crystal structure of survivin is quite reliable, as physiological conditions were used to obtain the images.
Little finger
The little finger, or pinky finger (in American English), also known as the fifth digit, or pinkie, is the most ulnar and smallest finger of the human hand, opposite the thumb, and next to the ring finger.
Stygotantulus
Another contender for the world's smallest arthropod is "Tantulacus dieteri", with a total body length of only .
Calcaneal fracture
The calcaneus, also known as the heel bone, is the largest of the tarsal bones and articulates with the cuboid bone anteriorly and the talus bone superiorly. It is responsible for transmitting the majority of the body's weight from the talus bone to the ground.
Bony-eared assfish
The bony-eared assfish holds the record for the smallest brain-to-body weight ratio of all vertebrates.
Smallest organisms
Nanobes are thought by some scientists to be the smallest known organisms 
about one tenth the size of the smallest known bacteria. Nanobes, tiny filamental structures first found in some rocks and sediments, were first described in 1996 by Philippa Uwins of the University of Queensland.
White-toothed shrew
The outer layer of these shrews' teeth is white, unlike that of the red-toothed shrews. These species are typically found in Africa and southern Europe and Asia. This subfamily includes the largest shrew, the Asian house shrew ("Suncus murinus"), at about 15 cm in length, and the smallest, the Etruscan shrew ("Suncus etruscus"), at about 3.5 cm in length and 2 grams in weight. Shrews are possibly the world's smallest extant mammal (although some give this title to the bumblebee bat). "Crocidura" contains the most species of any mammal genus.
Pisiform bone
The pisiform bone ( or ), also spelled pisiforme (from the Latin "pisifomis", pea-shaped), is a small knobbly, sesamoid bone that is found in the wrist. It forms the ulnar border of the carpal tunnel.
Talus bone
The second largest of the tarsal bones, it is also one of the bones in the human body with the highest percentage of its surface area covered by articular cartilage. Additionally, it is also unusual in that it has a retrograde blood supply, i.e. arterial blood enters the bone at the distal end.
Interparietal bone
In humans, it corresponds to the upper portion of the squama of the occipital bone that lies superior to the highest nuchal line and is completely fused to the supraoccipital. However, in some individuals this portion remains separate from the rest of the occipital bone throughout life. In such cases, this separate bone is particularly referred as Inca bone. Inca bones in humans were first found in the skulls of contemporary indigenous peoples of the southern Andes as well as in those of mummies of the Inca civilization. Although the Inca bone was originally encountered as a variation in South American and Latin American cranial remains, the variation occurs in people from all geographic regions of the world and is by no means indicative of South/Latin American origin.
Albertonykus
"Albertonykus" is the smallest known alvarezsaurid ever discovered in North America, measuring only 70 centimeters (2.5 ft) in length. Other estimates are 1.1 meters and 5 kg. Alvarezsaurs typically had slender hind legs, long rigid tails, and unusually short arms that were powerfully built to support a large claw. Although no skull bones of "Albertonykus" have been found, related animals from Mongolia show that they likely had long, slender snouts filled with tiny teeth similar to those of armadillos and anteaters. It is likely that "Albertonykus" ate insects, using its large thumb claw to tear open rotten logs to find its prey. As in other alvarezsaurs, the forelimbs of "Albertonykus" were specialized for digging, but were too short to permit burrowing. Unfortunately at this time the skeleton of "Albertonykus" is not complete, but its Mongolian relatives give us a distinct idea of what the rest of the skeleton would have looked like.
Nanobiomechanics
Most of the biological materials have different hierarchical levels, and the smallest ones refer to the nanoscale. For example, bone has up to seven levels of biological organization, and the smallest level, i.e., single collagen fibril and hydroxylapatite minerals have dimensions well below 100 nm. Therefore, being able to probe properties at this small scales provides a great opportunity for better understanding the fundamental properties of these materials. For example, measurements have shown that nanomechanical heterogeneity exists even within single collagen fibrils as small as 100 nm.
Bone
There are five types of bones in the human body: long, short, flat, irregular, and sesamoid.
Great saphenous vein
The great saphenous vein (GSV, alternately "long saphenous vein") is a large, subcutaneous, superficial vein of the leg. It is the longest vein in the body, running along the length of the lower limb, returning blood from the foot, leg and thigh to the deep femoral vein at the femoral triangle.
Stapedectomy
Laser stapedotomy is a well-established surgical technique for treating conductive hearing loss due to otosclerosis. The procedure creates a tiny opening in the stapes (the smallest bone in the human body) in which to secure a prosthetic. The CO laser allows the surgeon to create very small, precisely placed holes without increasing the temperature of the inner ear fluid by more than one degree, making this an extremely safe surgical solution. The hole diameter can be predetermined according to the prosthesis diameter. Treatment can be completed in a single operation visit using anesthesia, normally followed by one or two nights' hospitalization with subsequent at-home recovery time a matter of days or weeks.
Sartorius muscle
The sartorius muscle () is the longest muscle in the human body. It is a long, thin, superficial muscle that runs down the length of the thigh in the anterior compartment.
Ear
The pinna consists of a single piece of elastic cartilage with a complicated relief on its inner surface and a fairly smooth configuration on its posterior surface. A tubercle, known as Darwin's tubercle, is sometimes present, lying in the descending part of the helix and corresponding to the ear-tip of mammals. The earlobe consists of areola and adipose tissue. The symmetrical arrangement of the two ears allows for the localisation of sound. The brain accomplishes this by comparing arrival-times and intensities from each ear, in circuits located in the superior olivary complex and the trapezoid bodies which are connected via pathways to both ears.
The middle ear lies between the outer ear and the inner ear. It consists of an air-filled cavity called the tympanic cavity and includes the three ossicles and their attaching ligaments; the auditory tube; and the round and oval windows. The ossicles are three small bones that function together to receive, amplify, and transmit the sound from the eardrum to the inner ear. The ossicles are the malleus (hammer), incus (anvil), and the stapes (stirrup). The stapes is the smallest named bone in the body. The middle ear also connects to the upper throat at the nasopharynx via the pharyngeal opening of the Eustachian tube.
Navicular bone
The navicular bone is a small bone found in the feet of most mammals.
Lacrimal bone
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of the lacrimal bone function in the process of lacrimation or crying. Specifically, the lacrimal bone helps form the nasolacrimal canal necessary for tear translocation. A depression on the anterior inferior portion of the bone, the lacrimal fossa, houses the membranous lacrimal sac. Tears or lacrimal fluid, from the lacrimal glands, collect in this sac during excessive lacrimation. The fluid then flows through the nasolacrimal duct and into the nasopharynx. This drainage results in what is commonly referred to a runny nose during excessive crying or tear production. Injury or fracture of the lacrimal bone can result in posttraumatic obstruction of the lacrimal pathways.
Ulna
The ulna is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. It is broader close to the elbow, and narrows as it approaches the wrist.
Plantaris muscle
It is composed of a thin muscle belly and a long thin tendon. While not as thick as the achilles tendon, the plantaris tendon (which tends to be between 30 and 45 cm in length) is the longest tendon in the human body. Not including the tendon, the plantaris muscle is approximately 5–10 cm long and is absent in 8-12% of the population. It is one of the plantar flexors in the posterior compartment of the leg, along with the gastrocnemius and soleus muscles. The plantaris is considered an unimportant muscle and mainly acts with the gastrocnemius.
Bone
A bone is a rigid organ that constitutes part of the vertebrate skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions.
Heart
The size of the heart varies among the different animal groups, with hearts in vertebrates ranging from those of the smallest mice (12 mg) to the blue whale (600 kg). In vertebrates, the heart lies in the middle of the ventral part of the body, surrounded by a pericardium. which in some fish may be connected to the peritoneum.
Small intestine
The small intestine is a complex organ, and as such, there are a very large number of possible conditions that may affect the function of the small bowel. A few of them are listed below, some of which are common, with up to 10% of people being affected at some time in their lives, while others are vanishingly rare.
The small intestine is found in all tetrapods and also in teleosts, although its form and length vary enormously between species. In teleosts, it is relatively short, typically around one and a half times the length of the fish's body. It commonly has a number of "pyloric caeca", small pouch-like structures along its length that help to increase the overall surface area of the organ for digesting food. There is no ileocaecal valve in teleosts, with the boundary between the small intestine and the rectum being marked only by the end of the digestive epitheliu
In tetrapods, the ileocaecal valve is always present, opening into the colon. The length of the small intestine is typically longer in tetrapods than in teleosts, but is especially so in herbivores, as well as in mammals and birds, which have a higher metabolic rate than amphibians or reptiles. The lining of the small intestine includes microscopic folds to increase its surface area in all vertebrates, but only in mammals do these develop into true villi.
Smallest organisms
The Etruscan shrew ("Suncus etruscus"), is the smallest mammal by mass, weighing only about on average. The bumblebee bat has a smaller skull size. The smallest mammal that ever lived, the shrew-like "Batodonoides vanhouteni", weighed only .
Adductor minimus muscle
In human anatomy, the adductor minimus (adductor femoris minimus or adductor quartus) is a small and flat skeletal muscle in the thigh which constitutes the upper, lateral part of the adductor magnus muscle.
Fibular artery
At one point in its history, both the Greek term "perone" and the Latin term "fibula" were competing to describe the smaller bone of the leg. Many of the arteries, veins, nerves, and muscles in the leg are named according to what bone they are near (e.g. tibialis anterior and the tibial nerve are near the tibia). So the artery that runs near the smaller leg bone had two names: the "peroneal artery" and the "fibular artery". The term "fibula" eventually became the standard name for the bone, but many of the related arteries, muscles, and nerves are still called by the Greek derived name "peroneal". The Terminologia Anatomica, the international standard for anatomical nomenclature, states that both "fibula" and "perone" derived names are acceptable, but lists the "fibula" derived names as the preferred terms.
Cerebellar granule cell
Cerebellar granule cells form the thick granular layer of the cerebellar cortex and are among the smallest neurons in the brain. (The term granule cell is used for several unrelated types of small neurons in various parts of the brain.) Cerebellar granule cells are also the most numerous neurons in the brain: in humans, estimates of their total number average around 50 billion, which means that they constitute about 3/4 of the brain's neurons.
Osteoid osteoma
An osteoid osteoma is a benign bone tumor that arises from osteoblasts and was originally thought to be a smaller version of an osteoblastoma. Osteoid osteomas tend to be less than 1.5 cm in size. The tumor can be in any bone in the body but are most common in long bones, such as the femur and tibia. They account for 10 to 12 percent of all benign bone tumors. "Osteoid osteomas may occur at any age, and are most common in patients between the ages of 4 and 25 years old. Males are affected approximately three times more commonly than females."
Least bittern
The least bittern is one of the smallest herons in the world, with perhaps only the dwarf bittern and the black-backed bittern averaging smaller in length. It can measure from in length, and the wingspan ranges from . Body mass is from , with most least bitterns weighing between , making this perhaps the lightest of all herons. A recent manual of avian body masses cites another species in this genus, the stripe-backed bittern, as having a mean body mass slightly lower than the least bittern, which is credited with a mean mass of .
Axial skeleton
At birth the majority of humans have 33 separate vertebrae. However, during normal development several vertebrae fuse together, leaving a total of 24, in most cases. The confusion about whether or not there are 32-34 vertebrae stems from the fact that the two lowest vertebrae, the sacrum and the coccyx, are single bones made up of several smaller bones which have fused together. This is how the vertebrae are counted: 24 separate vertebrae and the sacrum, formed from 5 fused vertebrae and the coccyx, formed from 3-5 fused vertebrae. If you count the coccyx and sacrum each as one vertebra, then there are 26 vertebrae. If the fused vertebrae are all counted separately, then the total number of vertebrae comes to between 32 and 34.
Smallest organisms
The smallest vertebrates (and smallest amphibians) known are "Paedophryne amauensis" frogs from Papua New Guinea, which range in length from , and average . Previously, the title of smallest vertebrate was held by members of the fish genus "Paedocypris" of Indonesia.
Hip bone
The ischium forms the lower and back part of the hip bone and is located below the ilium and behind the pubis. The ischium is the strongest of the three regions that form the hip bone. It is divisible into three portions: the body, the superior ramus, and the inferior ramus. The body forms approximately one-third of the acetabulum.
Stapedius muscle
The stapedius is the smallest skeletal muscle in the human body. At just over one millimeter in length, its purpose is to stabilize the smallest bone in the body, the stapes.
Egg cell
The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a microscope or other magnification device. The human ovum measures approximately 0.1 mm in diameter.
Incisive bone
In human anatomy, the incisive bone or (Latin) os incisivum is the portion of the maxilla adjacent to the incisors. It is formed from the fusion of a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals. While Johann Wolfgang von Goethe was not the first one to discover incisive bone in the humans, he was the first to prove its presence across mammals. Hence, incisive bone is also known as Goethe's bone
In other animals the term "premaxilla" is more often used to refer to the incisive bone. Yet other terms include "premaxillary bone", "os premaxillare", "intermaxillary bone", and "os intermaxillare".
Operculum (fish)
The opercular series contains four bone segments known as the preoperculum, suboperculum, interoperculum and operculum. The preoperculum is a crescent-shaped structure that has a series of ridges directed posterodorsally to the organisms canal pores. The preoperculum can be located through an exposed condyle that is present immediately under its ventral margin; it also borders the operculum, suboperculum, and interoperculum posteriorly. The suboperculum is rectangular in shape in most bony fishy and is located ventral to the preoperculum and operculum components. It is the thinnest bone segment out of the opercular series and is located directly above the gills. The interoperculum is triangular shaped and borders the suboperculum posterodorsally and the preoperculum anterodorsally. This bone is also known to be short on the dorsal and ventral surrounding borders.
Brown bear
In linear measurements and mean body mass, several subspecies may vie for the title of smallest subtype, although thus far their reported body masses broadly overlaps with those of the smaller-bodied populations of Eurasian brown and grizzly bears. Leopold (1959) described the now-extinct Mexican grizzly bear that, according to Rausch (1963), as the smallest subtype of grizzly bear in North America, although the exact parameters of its body size are not known today. Bears from the Syrian subspecies ("U. a. syriacus") will reportedly weigh around in adulthood. The Himalayan brown bear ("U. a. isabellinus") is another rival for the smallest subspecies, in Pakistan this subtype averages about in females and in males. Himalayan brown bear females were cited with an average head-and-body length of merely . Brown bears of the compact Gobi Desert population, which is not usually listed as a distinct subspecies in recent decades, weigh around between the sexes, so are similar in weight to bears from the Himalayas and even heavier than grizzlies from Jasper National Park. However, the Gobi bear has been reported to measure as small as in head-and-body length, which if accurate would make them the smallest known brown bear in linear dimensions. These smallest brown bear subtypes are characteristically found in "barren-ground" type habitats, i.e. sub-desert in bears from the Syrian subspecies and the Gobi subtype and arid alpine meadow in Himalayan brown bears.