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The nervous system regulates visceral movement, glandular secretion, blood flow and coordinated bodily responses, while also influencing nutrition indirectly through those functions. Organic or vegetative life here means activities maintaining the body, such as blood circulation, digestion, pulmonary ventilation, secretion and excretion. It does not designate an independent form of living substance.

One influence is directly motor. Autonomic nerves alter the rate and force of the heart, contract or relax smooth muscle in the intestine, urinary bladder, airways and blood vessels, and coordinate movement with the opening and closure of sphincters. Their effect need not be excitatory: an active vagus nerve can slow the heart, while other pathways accelerate it. In the modern account, sympathetic and parasympathetic effects depend on the target and its receptors; they are not respectively universal accelerator and brake systems. Some organs receive both divisions, while others do not have a simple balanced double supply.^[ref]

A second influence is secretomotor. Activity in appropriate nerves can increase salivary secretion, alter gastric acid secretion and promote sweating. This is distinguishable from moving a duct or changing its calibre. A convincing experiment collects a secretion from a cannulated duct while a nerve is stimulated, rather than inferring secretion from a change of colour or organ size. For example, stimulation of the chorda tympani can evoke fluid from the submandibular gland. The response depends on functioning secretory biological cells; the nerve communicates a command rather than supplying the material constituents of saliva.

A third influence is vasomotor. Changing the calibre of arterioles changes local vascular resistance and perfusion. The classic comparison of an ear before and after interruption of its cervical sympathetic supply illustrates loss of vasoconstrictor tone: the vessels dilate and the ear becomes warmer because more warm blood reaches it. Stimulation of the peripheral cut pathway can produce the converse vascular effect. Warmth therefore need not mean that the local nerves themselves generate more heat. Vascular control also changes the delivery of oxygen and nutrients to a gland or tissue, so it can modify function indirectly.

These outputs are organized by sensory feedback and reflexes. Distension of the intestine can evoke coordinated movement; changes in blood pressure or blood-gas composition influence heart rate and breathing. Local circuits in the enteric nervous system permit some digestive activity without an intact connection to the brain, while longer reflexes involve the spinal cord or brainstem. Central states also matter: the sight or expectation of food can initiate preparatory digestive responses, and fear can alter heart rate, sweating and visceral movement.^[ref]

Somatic motor activity also supports vegetative functions. Breathing uses the respiratory diaphragm and other skeletal muscles; swallowing and continence use coordinated skeletal muscle as well as smooth muscle. Thus organic function cannot be identified solely with the anatomical distribution of the sympathetic nervous system.

The historical idea of a direct trophic influence requires discrimination. A denervation region may change through loss of movement, altered perfusion, loss of protective sensation or changed secretion. Those observations alone do not establish a special nutritive fluid flowing down the nerve. Modern biology recognizes molecular signalling between nerves and their targets, as well as neuroendocrine signalling pathways: the hypothalamus can influence hormone release, and sympathetic input can evoke adrenal medulla secretion. These are mechanisms added to, rather than evidence for an undefined historical nutritive force. A useful experimental design measures the motor, vascular and secretory consequences separately before assigning a residual effect to direct trophic action.

Chyle is intestinal lymph enriched with absorbed dietary lipids; its usual route ends in the venous circulation at the left jugulosubclavian junction. The milky appearance after a fat-containing meal is chiefly due to suspended lipid-rich particles, now called chylomicrons.

Formation begins with lipid digestion in the small intestine. Pancreatic lipase helps hydrolyse dietary triglycerides; bile salts help the digestion products reach the intestinal absorptive surface in mixed micelles. Enterocytes take up the products, reconstruct much of the long-chain triglyceride, and package it with other lipids and apolipoproteins into chylomicrons. These leave the basolateral side of the enterocytes and enter the central lacteals of the intestinal villi. Thus the particles carried in chyle are not simply intact globules of a meal passing through an open hole from the intestinal lumen.^[ref]

From the lacteals, chyle enters lymphatic channels in the intestinal wall and then collecting vessels in the mesentery. These vessels pass through mesenteric lymph nodes, with afferent vessels entering and efferent vessels leaving the nodes. Successive collectors join the intestinal lymphatic trunk or trunks. They usually communicate with the cisterna chyli, an expanded origin of the thoracic duct in the upper lumbar region, near the bodies of L1–L2 and to the right of the aorta. The cisterna chyli also receives lymph from lumbar trunks; the stream beyond it therefore contains material from more than the intestine. A conspicuous sac is not present in every individual.

The thoracic duct passes through the aortic hiatus of the respiratory diaphragm and ascends in the posterior mediastinum, typically between the aorta and azygos vein, behind the oesophagus. It crosses towards the left in the middle or upper thorax, continues to the root of the neck and arches to its terminal venous opening. The usual endpoint is the left venous angle, where the left internal jugular vein joins the left subclavian vein; terminal branches and the precise opening show anatomical variation. It is not normally the right venous angle or a direct entrance into the portal vein.^[ref]

The flow is promoted by intrinsic contraction of collecting lymphatic vessels, movements of surrounding muscles and respiratory changes of pressure. Lymphatic valves limit backward movement. Lymph nodes are interposed biological structures, not pumps that propel every particle independently.^[ref]

This route applies particularly to the long-chain dietary lipids carried by chylomicrons. Most absorbed glucose and amino acids, and much shorter-chain fatty acid material, follow portal vascular routes instead. Confusing these pathways would obscure the reason for asking separately about chyle. In a classical anatomical demonstration, the mesenteric channels of an appropriately fed animal appear white, and an injected or dissected preparation can trace their continuity towards the thoracic duct. The timing after a fatty meal matters: an empty-looking channel in a fasted preparation does not prove absence of a lymphatic vessel. The molecular account of chylomicrons is a modern explanation of the older gross observation.

In 1866, ovariotomy was justified for selected serious ovarian tumours when removal offered a better prospect than continued enlargement, repeated temporary drainage or progressive disability. The diagnosis, probable resectability, operative danger and the woman's informed preference all mattered.

Before recommending it, establish as far as contemporary examination allowed that the mass was ovarian rather than pregnancy, ascites, a uterine tumour or another abdominal lesion. Progressive enlargement, pain, pressure on the urinary bladder or intestine, difficulty breathing and loss of function strengthened the case for intervention. Repeated refilling after tapping showed why evacuation of a cyst's contents was often temporary palliation. A small tolerable mass, severe intercurrent disease, extreme exhaustion, extensive fixation or suspected widely disseminated disease altered the balance. It would be equally mistaken to operate on every abdominal swelling or to wait until avoidable debility made an otherwise feasible operation desperate.

The period operation can be described by its purposes and stages. Following preparation and anaesthesia, the surgeon opened the abdomen through a midline incision and identified the tumour. In a large cystic mass, a trocar and cannula could evacuate fluid under control so the mass could be delivered through a smaller opening. Adhesions had to be assessed and separated only as safely practicable, with particular care around the intestine, urinary bladder and vascular attachments. The tumour's pedicle was secured against haemorrhage, then the mass was detached. The operator inspected for bleeding, protected the abdominal contents and closed the wound; postoperative observation looked for haemorrhage, peritonitis, collapse and other complications. This is a historical operative description, not a present surgical instruction.^[ref]

Management of the pedicle was a central technical problem. Clamps, ligatures and cautery embodied different approaches to securing blood vessels and dealing with the stump. One period method retained a clamped pedicle externally at the wound; other methods differed. The apparatus mattered because inadequate control risked fatal haemorrhage, while devitalized tissue, contamination and its relation to the wound created other dangers. A 1866 discussion specifically compared modes of dealing with the pedicle; there was no single timeless “ovariotomy technique”.^[ref]

Modern correction: management of an ovarian mass begins with risk assessment, not automatic removal of an ovary. History, examination and ultrasonography, with selected laboratory investigations, guide observation, benign gynaecological treatment or referral to gynaecological oncology. Many simple cysts can be observed; symptomatic or suspicious masses may need surgery. Ovarian cystectomy may preserve ovarian tissue where appropriate, while suspected ovarian cancer requires specialist planning and attention to staging and avoiding unnecessary rupture or spillage. A modern oncological operation is not equivalent to the historical practice of decompressing a large cyst through a trocar.^[ref] Assessment of operative fitness, fertility wishes, the other ovary, alternatives and consent remains essential. Modern asepsis, haemostasis, anaesthetic care and postoperative support also prevent the historical risk estimates from being transferred directly to current practice.

Translation. Just as this great narrowness of the blood vessels, particularly in a body of this kind, had perhaps been the beginning of all the diseases, so I do not doubt that the hardness of the pancreas, and still more that of the duodenum, was the cause of the vomiting. For whether that portion of the intestine is constricted by compression, as Riolan long ago observed, whom you will see cited here in the Sepulchretum by Théophile Bonet, or whether, because its coats are scirrhous, it is quite unable to contract, these opposite causes are followed by the same effect: since the contents about to descend from the stomach are either less readily received or less readily propelled onwards, most of them remain in the stomach, and there, either becoming corrupted or simply troublesome and oppressive through their delay, provoke vomiting. The distinguished Molinelli has also published a clear example of this. The same thing must happen when the pylorus is affected by defects of the same kind.

You have very many examples here in the Sepulchretum by Théophile Bonet, as in Observations XI and XVII and most of the others following almost as far as XXVI, and again in LVI, §13; in the Additions, in Observations I and VIII; and indeed elsewhere, as in Book I, Section IX, not only in Observation XXXIV but also, if you attend to those “upturnings”, in XXXIII. Among those which you will read in this Section VIII, when you come to Observation XXI, not very unlike another supplied by Johannes Bohn, and find there that vomiting of all food and finally death within ten days followed blockage of the pylorus by a small silver coin which had been swallowed, you will undoubtedly recall that much larger silver coin which the skilful surgeon du Luc successfully dislodged from that place and indeed out of the body. He did so with other aids, but especially with mercury: pressing it onwards by its gravitational weight and reducing it by amalgamation, as the chemists call it, when pains near the pylorus had already begun, with an urge to vomit (the printed laevi at this point is unclear).

The central inference is that different impairments of passage can produce the same vomiting. The author is Giovanni Battista Morgagni; the extract corresponds to Book III, Letter XXX, article 13 of The Seats and Causes of Diseases Investigated by Anatomy by Giovanni Battista Morgagni. The opening haec, “this”, points back to an anatomical case preceding the selected extract. The translation preserves the difference between the tentative claim fortasse, “perhaps”, about the narrow blood vessels and the stronger non dubito, “I do not doubt”, about the cause of vomiting. It does not convert either level of historical confidence into a present-day demonstrated diagnosis. ^{[ref] [ref]}

The two mechanisms are not contradictory observations. Compression can narrow the entrance to the duodenum; hard, poorly contracting intestinal coats can fail to propel their contents onwards. Both impede gastric emptying, allowing retained material to provoke vomiting. This is an early example of connecting clinical observation with pathological anatomy. Nevertheless, gross hardness, described as scirrhous, does not by itself supply a modern microscopic diagnosis of scirrhous carcinoma. The descriptive term scirrhous hardening is therefore kept distinct from that modern category. The separate assertion about the pancreas likewise cannot identify its precise disease from this extract alone.

The Sepulchretum by Théophile Bonet is an earlier compilation of anatomical observations. Its cited observation numbers are retained because they are part of the argument's trail of evidence, including the distinction between Section VIII and the additional cross-reference to Book I, Section IX. Subversiones literally means “upturnings”; in this context the reference concerns disturbances or upheavals of the stomach, not a political meaning. Ventriculus here is the stomach, not a cardiac heart ventricle. The printed word laevi near the end is grammatically unclear in its context; the translation gives the secure surrounding sense and does not silently assign it a patient's identity, an anatomical side, or a new causal claim. ^{[ref] [ref]}

The coin episode reports an attempted mechanical and chemical remedy, not a modern recommended treatment. In the text, mercury is supposed both to press the coin onwards through its gravitational weight and to reduce it by amalgamation with its silver. The report does not establish the contribution of each mechanism, the extent of the coin's alteration, or therapeutic safety. Its purported success should not be generalized from a historical anecdote. Modern toxicological information distinguishes the chemical forms of mercury and their routes of exposure: swallowed liquid metal is poorly absorbed, whereas vapour is readily absorbed and can cause serious harm. This distinction neither validates the historical intervention nor warrants the false correction that any swallowed metallic mercury must immediately produce systemic poisoning. ^[ref]

Modern investigation also separates obstruction from impaired movement. Endoscopy uses a flexible instrument with a camera to inspect the upper digestive passage for structural abnormalities; a gastric emptying scintigraphy test instead follows a meal containing a small radioactive tracer with an external camera. These examinations illustrate how the proposed impediment to passage can now be tested rather than inferred from vomiting alone. They are later developments, not techniques available to the author of this passage. ^[ref]

The classical contrast is between ulceration centred on intestinal lymphoid tissue in enteric fever and granulomatous, often circumferential ulceration in intestinal tuberculosis. The historical expression continued fever covered more than one illness. The characteristic bowel lesions meant here point especially to typhoid fever; they should not be attributed indiscriminately to typhus or every prolonged fever.

In typhoid fever, Peyer's patches and solitary lymphoid follicles, particularly in the terminal ileum, enlarge and become infiltrated. Their breakdown and necrosis lead to sloughing and ulceration. The larger ulcers characteristically follow the long axis of the intestine, reflecting the shape of the affected aggregated lymphoid patch on the side opposite the mesentery. Depending on their stage, one may see swollen patches, necrotic sloughs, open ulcers or healing surfaces. Depth varies; erosion into a blood vessel can cause haemorrhage, while full-thickness destruction can cause intestinal perforation and peritonitis.

Microscopically, the important cellular component includes swollen macrophages with ingested organisms and cellular debris; this is not simply a dense collection of neutrophils forming an ordinary abscess. The surrounding mucosal architecture may become severely disturbed. These current cellular descriptions refine the gross lesion recognized before the causative organism was identified.^[ref][ref]

In historical phthisis, bowel disease frequently meant intestinal tuberculosis associated with pulmonary tuberculosis. Lesions commonly involve the terminal ileum and ileocaecal region, although other sites occur. Nodules in mucosal or submucosal lymphoid tissue undergo caseous necrosis, coalesce and break through the mucosa. The ulcerated surface tends to spread transversely and may encircle the bowel. The edges can be irregular and undermined, with additional tuberculous granulomas in the wall, serosal surface or draining lymph nodes. Progressive fibrosis may narrow the lumen and produce a stricture; thickened masses as well as ulcers can occur.^[ref]

A section from a tuberculous ulcer may show central caseous necrosis bordered by epithelioid macrophages, giant cells and lymphocytes. A section from an enteric-fever ulcer instead emphasizes destruction of lymphoid patches with macrophage-rich infiltration. A practical anatomical examination records site, orientation, depth, edges, intervening mucosa, serosal nodules and draining lymph nodes, rather than judging one detached fragment in isolation.

Longitudinal lymphoid-patch ulcers favour the classical enteric-fever pattern; transverse, caseating and often stenosing lesions favour intestinal tuberculosis. These are useful patterns rather than absolute rules. Modern microbiological culture, organism-specific molecular tests and appropriately sampled histology can establish the cause when gross appearances overlap.

The liver is both a metabolic processing organ and the producer of bile. These functions must be distinguished: much of what the liver contributes to the body enters the blood, whereas bile is its secretion into the digestive system.

Portal venous blood brings absorbed materials from the alimentary organs to the liver, while the hepatic artery supplies oxygenated blood. Within the hepatic sinusoids, the incoming blood encounters hepatocytes and scavenging Kupffer cells. Hepatocytes take up, transform, store and release substances; their bile canaliculi conduct bile towards the bile ducts. The organ's position therefore makes it a useful regulator between absorption from a meal and supply to the rest of the body.

Its main non-biliary functions include the following:

This modern list extends beyond the knowledge and biochemical vocabulary of 1867. It is consistent with the organ's combined metabolic, storage and clearance roles, rather than treating bile production as the whole explanation.^[ref]

Bile contains water, electrolytes, bile salts, phospholipids, cholesterol and bilirubin conjugates. Hepatocytes form the primary secretion; ductal epithelium modifies it. The gallbladder stores and concentrates bile between meals and releases it into the duodenum. Production of bile must therefore be distinguished from its intermittent delivery to a meal.

Its two central functions are assistance with lipid digestion and nutrient absorption, and excretion of selected waste substances. Amphipathic bile salts help disperse dietary fat and form mixed micelles carrying products of lipid digestion to the absorptive surface of the small intestine. They thereby promote uptake of fatty acids, monoglycerides, cholesterol and fat-soluble vitamins. Bile is not itself a source of pancreatic lipase, nor does emulsification chemically hydrolyse triglycerides. Biliary bilirubin, produced through haem breakdown, provides an excretory route; cholesterol and selected other substances also leave in bile. Most secreted bile salts are recovered, especially in the terminal ileum, and return through the portal vein: the enterohepatic circulation conserves the useful detergent.^[ref]

Two comparisons reveal why both sorts of function matter. First, compare a fresh liver extract with an extract prepared after an appropriate controlled interval: testing for reducing sugar and isolating glycogen distinguishes a stored precursor from newly liberated glucose. A reliable interpretation needs prompt sampling and controls because post-mortem glycogenolysis can change the result after the animal has died; detecting sugar in an organ alone does not prove where all of it was made. Secondly, in classical biliary fistula observations, diverting bile away from the intestine while collecting it separately allowed its output to be measured and the loss of normal fat assimilation to be examined. Comparing faecal fat with and without delivery of bile distinguishes a digestive contribution from a merely excretory one. The modern explanation is that loss of intestinal bile salts impairs mixed micelle formation, while jaundice from retained biliary pigment is a separate consequence of failed pigment elimination.

Entozoa is a historical grouping of internal animal parasites, especially parasitic worms; it is not a single natural modern clade. The core human examples belong principally to the flatworms, including Cestoda and Trematoda, and to the roundworms, or Nematoda. The distinction is structural and developmental, not merely between inhabitants of the intestine and inhabitants of other organs.

The nineteenth-century higher arrangement was unsettled. Schemes placed these animals within Vermes, or within annuloid assemblages that included other supposedly related simple invertebrates. For a specifically pre-exam example, the 1865 geological-museum classification put Entozoa in Annuloida, within Annulosa. These historical groups must not be equated with the modern Annelida: an Ascaris lumbricoides is not an earthworm. A more useful subdivision for this answer is the four orders treated in Thomas Spencer Cobbold's 1864 Entozoa, an Introduction to the Study of Helminthology by Thomas Spencer Cobbold: Trematoda, Nematoda, Acanthocephala and Cestoda.^[ref][ref]

The leading distinctions are as follows:

For a British medical answer of this period, the ordinary intestinal list should begin with the following species; the modern life-cycle details clarify their identities rather than claiming that every step was already established in 1867:

Important tissue examples extend the answer beyond intestinal adults. The historical Trichina spiralis is Trichinella spiralis: ingested infected meat carries larvae, adults develop in the small intestine, and new larvae migrate to skeletal muscle. This is a distinct developmental pattern from the egg-acquired intestinal Ascaris lumbricoides infection.^[ref] Human hydatids are the larval hydatid cysts of Echinococcus, classically the Echinococcus granulosus complex; the small adult tapeworm is in a canid, while humans accidentally occupy the intermediate host role, commonly with liver or lung cysts.^[ref]

A crucial distinction is that human Taenia solium cysticercosis follows ingestion of eggs; eating pork containing cysticerci produces intestinal taeniasis. The historical name Cysticercus cellulosae designates a larval form, rather than an additional independent species to add to the list.^[ref]

Geographical qualification matters: Ancylostoma duodenale, Dracunculus medinensis and Schistosoma haematobium are important in their endemic settings; Fasciola hepatica is a familiar liver fluke but is not an ordinary common human worm in Britain. An enumeration should not turn this into a claim that all named species are equally common in every population.^{[ref][ref][ref][ref]} Conversely, calling only the familiar intestinal adults Entozoa would omit the instructive tissue stages and their transmission.

The decisive experimental insight is continuity of development. Comparing eggs, tissue larvae and adults, and tracing transfer between appropriate hosts, demonstrates a life cycle rather than spontaneous generation within a patient. In diagnostic material, an adult attachment organ, a proglottid, an egg and a tissue cyst answer different identification questions. Identification therefore depends on the stage and the material actually supplied.

Translation. For rapidly developing, or acute diseases, also resolve of their own accord, sometimes through favourable chance and sometimes through nature's favour. Consequently, ignorant people, carried away by this, often avoid physicians and attribute these favourable outcomes to new incantations and amulets, or to chance; for these rapidly developing diseases are driven out either by a flow of sweat, by blood discharged through the nose, or by a discharge from the intestines. But chronic diseases, or diseases of slow development, which have already gained possession of the body with a kind of prior claim, call for the skill of the physician alone, since they are resolved neither by nature nor by chance.

Interpretation. Caelius Aurelianus contrasts spontaneous resolution in acute disease with the entrenched course of chronic disease. Here passiones means affections or diseases, not emotions; ligamenta means protective bindings or amulets, not anatomical ligaments; proventus means favourable outcomes. The metaphor praejudicio quodam gives the established disease something like a prior claim on the body. The final assertion is the author's defence of professional medicine, not a present-day law that every chronic disease requires effective medical treatment or that none can remit spontaneously. The account of sweating, nosebleeds and intestine discharge describes his historical explanation, not evidence that deliberately producing these discharges cures acute disease. ^[ref]

Vomiting is a coordinated nervous motor act that can be initiated from the digestive system, circulating emetic substances, the vestibular system, or higher and lower brain pathways. A cause need not lie in the stomach.

Local causes include irritant food or poisons, gastritis, gastroenteritis, gastric outlet obstruction and intestinal obstruction. Chemical irritation, inflammation or distension activates visceral sensory pathways, notably afferents of the vagus nerve, which relay to the medulla oblongata. In obstruction, retention and distension provide continuing stimulation; merely seeing food return does not imply excessive gastric contractile strength. Peritonitis and painful disease elsewhere in the abdomen can also recruit visceral afferent pathways.^[ref]

Circulating emetic agents, including some drugs and metabolic products accumulating in kidney failure, act partly through the area postrema, a chemosensitive region with unusually direct access to substances in the blood. Gastrointestinal and blood-borne inputs converge through the nucleus tractus solitarius and connected medullary networks. It is more accurate to describe interacting groups of neurons than one isolated “vomiting centre”.^[ref]

Other important groups are motion sickness, where information from the vestibular system conflicts with other sensory information; migraine and intracranial disease, including raised intracranial pressure from a brain tumour or intracranial haemorrhage; and higher-centre influences such as a repulsive sight, smell, fear or learned association. Pregnancy-associated vomiting belongs in the differential, with endocrine and central contributions rather than an explanation that it is simply mechanical pressure by the uterus upon the stomach. These causes engage different inputs to an overlapping final motor programme.^[ref]

The act itself requires several coordinated changes. The proximal stomach and lower oesophageal sphincter relax; retrograde activity can bring contents of the upper intestine into the stomach; the diaphragm and abdominal muscles generate a pressure gradient that expels the contents. During expulsion the upper passage opens while coordinated laryngeal closure helps protect the airway. Retching and actual expulsion are related stages, and neither should be confused with effortless regurgitation.^[ref]

This mechanism explains the diversity of causes: many sensory and chemical inputs can recruit the same coordinated output. A pressure recording and observation of gastrointestinal movements during an emetic response can distinguish the patterned act from a simple spontaneous return of contents; they would not, without further evidence, identify the original cause in an individual.

A hydrocele contains fluid around the testis; a scrotal hernia contains abdominal contents that have descended through the inguinal canal. Their distinction rests on a combination of location, continuity with the inguinal canal, behaviour and light transmission.

The usual acquired hydrocele is a collection between the layers of the tunica vaginalis. A scrotal hernia is generally an indirect inguinal hernia: a sac of peritoneum, often containing intestine or omentum, follows the spermatic cord into the scrotum. Persistence of the processus vaginalis can permit either a communicating hydrocele or an indirect inguinal hernia, depending on the communication and its contents. Thus the underlying developmental route is related even though the usual clinical appearances differ.^[ref]

If examination leaves doubt, ultrasonography can establish whether the swelling contains fluid, intestine or a solid tumour, assess the testis and show continuity with the inguinal canal. A collection may obscure a diseased testis; demonstrating fluid does not finish the diagnostic task. Blind puncture is not an appropriate diagnostic shortcut when a hernia remains possible. Even an established hydrocele usually reaccumulates after simple aspiration, which also risks infection.^[ref]

The vitelline duct connects the embryonic intestine to the yolk sac. In normal human development this connection narrows and disappears as the gut and surrounding structures mature.

Persistence of all or part of the connection can produce different anatomical remnants. Following the original connection explains why a remnant can occur at the intestinal side, the umbilical side or along the intervening route.^[ref]

The yolk sac is an extraembryonic structure associated with the embryonic gut. In yolk-rich eggs it mediates access to stored nutrients; the human yolk sac also has early developmental roles despite not containing a large yolk store.

Those roles include early blood formation and contributions associated with the developing gut and germ-cell lineage. The vitelline duct connects it with the embryonic intestine during a stage of development, so its name alone does not describe every function or the persistence of the connection.^[ref]