Scientific Illustration

biomedicalephemera:

Cross-section of human heart, displaying heart valves, chordae tendineae, and papillary muscles

Have you ever heard the expression “Tugging on your heart-strings”? Well, it’s not completely metaphorical, at least in terminology. There are literally parts of your heart known colloquially as “heart strings”, which have been described in an anatomical sense as far back as Vesalius. 

These “heart strings” are more properly called chordae tendineae. You can see them in the illustration, looking like thin wires or netting within the ventricles. They  start at the atrioventricular heart valves (the bicuspid or mitral and the tricuspid), and connect to the papillary muscles near the apex of the heart. The collagenous structure of these strings imparts to them a high level of strength, and the papillary muscles combined with some elastin give a high level of flexibility. they’re what keep your heart valves from everting (prolapsing) when the blood moves from the atria to the ventricles.

See, the valves have no muscular structure of their own, but work because the pressure of the blood pushing against them makes them open and close taut. But if the chordae tendineae weren’t there, that same pressure that makes sure they shut well also means that their fibrous structure would end up simply turning inside-out, and the blood would flow back into the atria, instead of to the lungs or the rest of the body. Insufficiency of the heart strings is one of many possible causes of mitral prolapse and valve insufficiency (leaky valves).

Anatomy: Descriptive and Surgical. Henry Gray, 1900.

biomedicalephemera:

Physalia pelagica [Physalia physalis] - The Portuguese Man-o-War

All the fascinating biological facts about the Portuguese Man-O-War aside, did you know that its name was actually coined as a derisive snipe at the Portuguese navy? Powerful and feared for centuries, they were in a period of steep decline during the 19th century. The appearance of the Man-O-War, especially when washed ashore, struck mid-century English explorers as a capsizing ship, or a sail with no boat to propel. 

In the end, I wouldn’t call the name completely derogatory. This siphonophore is the epitome of pain for most people who encounter them…they may look goofy, but unless you’re a loggerhead turtle, blue sea slug, or blanket octopus, it’s still not much to laugh at. The first two creatures eat these guys as a main part of their diet, and the blanket octopus is apparently *crazy* and will rip tentacles off of the Man-O-War, waving them around as a defensive measure.

Animaux Venimeux et Venins. Marie Phisalix, 1922.

biomedicalephemera:

Pieds d’Oiseaux - The Feet of Birds

You can clearly see the wide range of foot structures found in the Neornithes, and the intended usage of some of them is pretty obvious. When it comes to classifying the foot structure of birds, there are several characteristics that are noted, but the defining factor is the orientation of the digits (toes). Birds generally have four toes.

One term you might not know that’s important is the hallux - this is the innermost (“first”) digit of the foot, homologous to the big toe in humans. In birds, it often points backwards. It’s sometimes very well-developed (such as in perching birds), and sometimes so small it’s almost absent.

Anisodactyly (“unequal digit”) - This configuration is basically the standard. The three toes face forward, with the hallux facing backwards, so as to let the bird perch. This is present in songbirds and perching birds. Hawks, eagles, and falcons also have this configuration.

Syndactyly (“same digit”) - The third and fourth toes (outer and middle) are united for much of their length, and have a broad sole in common. You can see this in the kingfisher and the bee-eaters.

Zygodactyl (“yoke digit”) - The toes are arranged with digits 2 and 3 facing forwards, and digits 1 and 4 facing backwards. You can see this in parrots, woodpeckers, and roadrunners.

Heterodactyl (“different digit”) - Toes 1 and 2 are facing back, with 3 and 4 facing forward. This is only found in trogons.

Pamprodactyl (“Every digit”) - All four digits face forward, only found in swifts - this is a somewhat contested classification, as it’s believed that no birds use this as a primary configuration, even if swifts have been observed using it during their rare landings.

There are other useful terms when classifying birds by their foot structure, that have more to do with the type of bird itself, rather than the configuration of its bones. These classifications can include birds with more than one dactylous configuration.

Raptorial - Feet like the raptors and owls. These are strong, deeply cleft, with sturdy talons, meant for grasping and ripping.

Semipalmate - “Half-webbed” feet, where the anterior toes are only partially webbed. The Semipalmated Plover is a bird with these feet.

Totipalmate - “Fully webbed” feet, with all four toes united by one web - these are found on birds like cormorants.

Palmate - “Webbed” feet. These are your “basic” webbed feet - the three front toes are united, like in gulls and ducks. The fourth digit is not connected to the web.

Lobate - A swimming foot with a series of lobes along the toes. Found in birds like grebes.

Tableau Elementaire de l’Histoire Naturelle des Animaux par Georges Cuvier. 1798.

biomedicalephemera:

Forearm of Giant Armadillo - Dasypus gigas (now Priodontes maximus)

Look at those crazy claws! The giant armadillo actually walks on that third digit. Though it walks “normally” on its hind legs, the fore-body weight rests on just those two giant scratchers. They developed that way to help the armadillo dig, but apparently they work for walking on, too…what happens if they break a nail?

• Nomenclature (obsolete):

1. Dasypus - From Ancient Greek dasupous, meaning “rough-foot” - though the -pus in the genus name can be elucidated to mean “foot,” das(y/u)- is not a commonly-used prefix and is not listed in most Greek/Latin root references.
2. (Dasypus) gigas - Gigas - from the Ancient Greek gigas, meaning “giant”. However, gigas CURRENTLY means “a billion.” When the name of the genus was changed in the 1950s, the species name was changed, too, as the currently-accepted definition of gigas was no longer appropriate.
3. Dasypus gigas - “Giant Rough-Foot”

• Nomenclature (current):

1. Priodontes: Prio - from the Latin prior - “before”, -dontes, from dent/dont, “tooth” - so Prio - dontes means “before teeth” - refers to the fact that the genus is completely toothless.
2. (Priodontes) maximus: Maximus - from Latin maximum - “greatest, largest”, which is the superlative form of magnum - “great, large”.
3. Priodontes maximus = “Largest before teeth”

On the Anatomy of Vertebrates: Vol II - Birds and Mammals. Richard Owen, 1866.

biomedicalephemera:

Dide[l]phis derbiana (now Caluromys derbianus) - Derby’s Opossum

This Paraguayan and Central American opossum was named in honor of the 13th Earl of Derby.

This particular specimen lived in the Zoological Society’s Gardens, and would viciously attack anyone who came near her when she had young who were not yet on their own. When she was not with her young, she was shy, but not eager to attack.

Biologia centrali-americana: Mammalia. Edward Richard Alston, 1882.

biomedicalephemera:

Anatomy of the porpoise

The word “porpoise” comes from porcopiscus - Medieval Latin for “pig fish”. It was obviously related to dolphins, but with a snub-nose, it was more pig-like than the “delphinos” - ”fish with a womb”. Later, the English term “mereswine” was used to refer to both dolphins and porpoises.

Transactions of the Zoological Society of London. Vol VIII, 1878.

kaleidoscopicfable:

Origin of the phrase Sardonic grin.