34.3A: Ingestion - Biology

34.3A: Ingestion - Biology

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The first step to obtaining nutrition is ingestion, a process where food is taken in through the mouth and broken down by teeth and saliva.

Learning Objectives

  • Describe the process of ingestion and its role in the digestive system

Key Points

  • Food is ingested through the mouth and broken down through mastication (chewing).
  • Food must be chewed in order to be swallowed and broken down by digestive enzymes.
  • While food is being chewed, saliva chemically processes the food to aid in swallowing.
  • Medications and harmful or inedible substances may be ingested as well.
  • Pathogens, such as viruses, bacteria, and parasites, may be transmitted via ingestion, causing diseases like hepatitis A, polio, and cholera.

Key Terms

  • ingestion: consuming something orally, whether it be food, drink, medicine, or other substance; the first step of digestion
  • bolus: a round mass of something, especially of chewed food in the mouth or alimentary canal
  • mastication: the process of chewing


Obtaining nutrition and energy from food is a multi-step process. For animals, the first step is ingestion, the act of taking in food. The large molecules found in intact food cannot pass through the cell membranes. Food needs to be broken into smaller particles so that animals can harness the nutrients and organic molecules. The first step in this process is ingestion: taking in food through the mouth. Once in the mouth, the teeth, saliva, and tongue play important roles in mastication (preparing the food into bolus). Mastication, or chewing, is an extremely important part of the digestive process, especially for fruits and vegetables, as these have indigestible cellulose coats which must be physically broken down. Also, digestive enzymes only work on the surfaces of food particles, so the smaller the particle, the more efficient the digestive process. While the food is being mechanically broken down, the enzymes in saliva begin to chemically process the food as well. The combined action of these processes modifies the food from large particles to a soft mass that can be swallowed and can travel the length of the esophagus.

Besides nutritional items, other substances may be ingested, including medications (where ingestion is termed oral administration) and substances considered inedible, such as insect shells. Ingestion is also a common route taken by pathogenic organisms and poisons entering the body.

Some pathogens transmitted via ingestion include viruses, bacteria, and parasites. Most commonly, this takes place via the fecal-oral route. An intermediate step is often involved, such as drinking water contaminated by feces or food prepared by workers who fail to practice adequate hand-washing. This is more common in regions where untreated sewage is prevalent. Diseases transmitted via the fecal-oral route include hepatitis A, polio, and cholera.

Signs and symptoms of exposure

Following is a list of signs and symptoms that may be encountered in a person exposed to sodium azide. Signs and symptoms are not listed in order of importance, presentation or specificity. Also, partial presentations (an absence of some of the following signs/symptoms) do not necessarily imply less severe disease.

Central nervous system signs and symptoms

  • Agitation
  • Coma
  • Convulsions
  • Dizziness
  • Headache
  • Loss of consciousness (sudden collapse)

Respiratory signs and symptoms

  • Bradypnea (decreased respiratory rate)
  • Chest pain
  • Dyspnea (shortness of breath)
  • Hyperpnea (increased respiratory rate/depth)

Cardiovascular signs and symptoms

  • Bradycardia (decreased heart rate)&mdash late
  • Flushing
  • Hypertension (high blood pressure)&mdash early
  • Hypotension (low blood pressure)&mdash late
  • Tachycardia (increased heart rate)&mdash early

Gastrointestinal signs and symptoms

Other signs

Laboratory findings suggestive of sodium azide poisoning

  • Metabolic acidosis
  • Elevated anion gap
  • Increased plasma lactate concentration

Differential diagnosis &ndash poisoning with

  • Carbon monoxide
  • Cyanide
  • Ethylene glycol
  • Fluoroacetate
  • Hydrogen sulfide
  • Methanol
  • Phosphine

Note: The actual clinical manifestations of an exposure to sodium azide may be more variable than the syndrome described in this document.

Overview of global status of plastic presence in marine vertebrates

Marga L. Rivas, CECOUAL University of Almería, Almería, Spain.

CECOUAL Scientific Collection Centre, University of Almería, Almería, Spain

CEIMAR Marine Campus of International Excellence, UAL-UCA, Almeria, Spain

CEIMAR Marine Campus of International Excellence, UAL-UCA, Almeria, Spain

Biology Depart, Faculty of Ciencias del Mar y Ambientales, University of Cadiz, Cadiz, Spain

Macquarie University, Sydney, NSW, Australia

CECOUAL Scientific Collection Centre, University of Almería, Almería, Spain

CEIMAR Marine Campus of International Excellence, UAL-UCA, Almeria, Spain

Universidad Central “Marta Abreu de las Villas”, Santa Clara, Cuba

Marga L. Rivas, CECOUAL University of Almería, Almería, Spain.


The presence of plastic in the environment is generating impacts on all habitats and has become a major global problem in marine megafauna. Macroplastics can cause entanglement, ingestion and loss of suitable habitats. In addition to entanglement problems, there is evidence that plastics are entering the food web through ingestion by marine organisms, which could ultimately be affecting humans. Much of the available information on the impact of plastic in biota is scattered and disconnected due to the use of different methodologies. Here, we review the variety of approaches and protocols followed to assess macro- and microplastic ingestion in marine vertebrates such as sea turtles, cetaceans and fishes in order to offer a global overview of their current status. The analysis of 112 studies indicates the highest plastic ingestion in organisms collected in the Mediterranean and Northeast Indian Ocean with significant differences among plastic types ingested by different groups of animals, including differences in colour and the type of prevalent polymers. In sea turtles, the most prevalent types of plastics are white plastics (66.60%), fibres (54.54%) and LDPE polymer (39.09%) in cetaceans, white macro- and microplastics (38.31%), fibres (79.95%) and PA polymer (49.60%) and in fishes, transparent plastics (45.97%), fibres (66.71%) and polyester polymer (36.20%). Overall, clear fibre microplastics are likely the most predominant types ingested by marine megafauna around the globe.

DNA Methyltransferase 1 and 3a Expression in the Frontal Cortex Regulates Palatable Food Consumption

DNA methylation is an important regulatory mechanism in the control of neuronal function. Both during development and following exposure to salient stimuli, plasticity in the methylation of cytosine residues leads to a change in neuron excitability that subsequently sculpts animal behavior. However, although the response of DNA methyltransferase enzymes in adult neurons to stimuli such as drugs of abuse have been described, less is known about how these enzymes regulate methylation at specific loci to change the drive to ingest natural rewards. Specifically, we do not understand how changes in methylation within important brain areas known to regulate palatable food intake can affect ingestion, while a detailed investigation of the neurophysiological and genomic effects of perturbing methyltransferase function has not been pursued. By deleting DNA methyltransferase 1 and 3a in the mouse prefrontal cortex, we observed the requirement for these enzymes in the regulation of nutrient rich food consumption in the absence of any effect on the intake of low fat and low sugar chow. We also determined that the deletion profoundly affected neuron excitability within pyramidal cells resident in superficial layers II/III of the cortex but had little effect in deep layer V neurons. Finally, reduced representation bisulfite sequencing revealed both hypo and hypermethylation in response to methyltransferase deletion, an effect that was observed in binding sites for retinoic acid receptor beta (RARβ) located within regulatory regions of genes known to affect neuronal function. Together, our data suggest that alterations in the actions of RARβ could shift neuronal activity to reduce palatable food intake.

What is Egestion?

After the ingestion, the food is digested and the nutrients are absorbed through the gastrointestinal tract. After this processes, the remaining waste should be removed from the body. The removal of this waste from the body is called egestion. In most multicellular organisms, the egestion takes place through the anus, whereas in unicellular organisms it takes place via cell membranes. However, in animals with the incomplete digestive tract that lack anus, the egestion is taken place through the mouth or via body cells. The food material waste of most multicellular organisms including humans is usually in the form of semi-solid, which is known as feces. Feces mainly consists of fiber, undigested food, living and dead bacteria, water, fat, inorganic matter and proteins. The semi-solid texture is due to the low water content as the large intestine absorb the maximum amount of water before feces is egested. The color and texture of the feces mainly depend on the state of the digestive system, health condition, and diet. Waste is stored temporarily in the rectum of the gastrointestinal tract until it is egested. Egestion is controlled by anal sphincter.

Whiplash Injury


Exercises for patients with whiplash can be divided into active ROM (AROM) exercises, postural exercises, spinal stabilization exercises, balance/proprioception exercises, and cardiovascular exercises.

AROM Exercises

After the initial supine exercises aimed at encouraging movement, therapists should progress AROM exercises in a weightbearing (upright) position and during functional tasks. AROM exercises should aim to engage all planes of movement and be performed into slight resistance or discomfort. A stretch, ache, or pain does not signal damage but rather the sensitivity of the tissue. By slowly “nudging” the exercises into slight discomfort, AROM will improve. Exercises that stop short of pain will over time cause patients to decrease their movement, whereas the “no pain, no gain” mantra leads to “boom-bust” cycles in which patients ignore pain and pay for it in the days to follow. Over time this model will also cause patients to move less.

Postural Exercises

It is common for patients with whiplash to present with a forward head, rounded shoulder posture after a whiplash injury. Pain inhibition, protective mechanisms, and fear cause the patient to adopt a posture of comfort or safety. This is normal. Anterior cervico- thoracic muscles develop adaptive shortening, whereas posterior thoracic muscles tend to lengthen and become weak, leading to postural changes ( Drescher et al. 2008 ). Therapists should develop exercises aimed at stretching shortened overactive muscles, while working on strengthening weak muscles. Therapists should also encourage patients to routinely check posture throughout the day with cues such as a cell phone ringing or signing on to check e-mail.

Spinal Stabilization Exercises ( Sterling et al. 2003b )

There is a large body of research regarding segmental spinal stabilization in the lumbar spine. Similar research is now emerging about the cervical spine ( Jull et al. 2007, Sterling et al. 2003b ). The cervical spine helps support and orient the head in relation to the thoracic spine and provides two key elements: stability and mobility. Similar to the lumbar spine, the deeper muscles closer to the spine contribute to stability, whereas the larger, superficial muscles that span multiple joints contribute more to movement. The deeper muscles have control strategies and proper morphology to stabilize the neck. In healthy individuals, the deep neck flexors provide a low-level, tonic contraction prior to movement of the extremities to protect the cervical spine. However, following injury, several changes occur to the deep cervical flexors:

Reduced activation of the deep neck flexors

Augmented superficial muscle activity

Change in feedforward activity

Prolonged muscle activation after voluntary contraction

Reduced relative rest periods

Change in muscle fiber type from type I (slow twitch) to type II (fast twitch)

Fatty tissue infiltration

Changes in fiber/capillary ratios

All of these changes indicate that patients with neck pain (i.e., WAD) will demonstrate limited endurance, greater fatigability, less strength, altered proprioception, and reorganized motor control. The cranio-cervical flexion test (CCFT) is used to evaluate the ability of the deep cervical flexors to produce low-load tonic submaximal contractions ( Fig. 71.3 ) ( Jull et al. 2008 ). Therapists should concentrate part of the rehabilitation of the patient with whiplash to retraining the deep neck flexors of the cervical spine. These exercises should aim to provide protection to the cervical spine during ADLs. Once local stabilizers have been activated and retrained, therapists should have patients perform various exercises incorporating weights and resistive bands while engaging the deep neck flexors. Stabilization exercises should focus on low-load, tonic contractions, which should be progressed by increasing the time the patient contracts the deep neck flexors (their endurance, in other words).

Proprioception/Balance Exercises

The previous section on spinal stabilization describes the function of the cervical spine muscles as a means to help orient the head in space. Studies have shown that patients with WAD and patients with mechanical neck pain have difficulty repositioning their head in space. Because the cervical spine muscles not only contribute to segmental control but also head positioning, therapists should evaluate and treat joint positioning errors. Therapists should develop exercises that help retrain balance and proprioception by increasingly challenging the postural system (i.e., altering foot position and visual input).

Cardiovascular Exercises

Therapists should help patients develop a home exercise program that includes aerobic exercise. The neurophysiologic mechanisms behind aerobic exercise include increasing blood flow and oxygenation of muscles and neural tissue, regulating stress chemicals such as adrenaline and cortisol, boosting the immune system, improving memory, decreasing sleep disturbance, and providing distraction.

Plastic ingestion by fish a growing problem

The consumption of plastic by marine animals is an increasingly pervasive problem, with litter turning up in the bellies of wildlife as varied as mammals, birds, turtles and fish. However, according to a research review by ecologists at Stanford University’s Hopkins Marine Station and PhD student Alex McInturf at UC Davis, the problem is impacting species unevenly, with some more susceptible to eating a plastic dinner than others. With billions of people around the world relying on seafood for sustenance and financial security, this research, published Feb 9. in the journal Global Change Biology, warns that there is a growing number of species – including over 200 species of commercial importance – eating plastic.

Matthew Savoca was collecting data on plastic ingestion by seabirds for his PhD when he became interested in uncovering ecological traits linked to increased consumption. Now, as a postdoctoral research fellow at the Hopkins Marine Station, he has conducted one of the most comprehensive analyses of plastic ingestion on fish ever performed.

“Fish are a really good species to track the flow of plastic pollution through marine ecosystems,” said Savoca, who is lead author of the paper. “Now, we are showing the numbers in ways they haven’t been shown before. No previous studies have looked across all of this research for broad patterns and drivers.”

Savoca and his team collected all the data they could find from scientific literature related to plastic ingestion by fish. In total, they reviewed 129 studies on 171,774 individuals of 555 species of marine fish. When he first began this endeavor roughly a decade ago, he was surprised how little data was available. However, over the last few years, Savoca said, the number of studies has “gone through the roof.”

The team’s database reveals the consumption of plastic by fish is widespread and increasing. Over the last decade, the rate of plastic consumption has doubled, increasing by 2.4 percent every year. Part of this is due to scientists’ increasing ability to detect smaller particles of plastic than before.

“Don’t panic, because unlike other environmental issues, we have an impassioned public movement to do something about it,” said Savoca. “This is half the battle, but we must keep it going.”

Although this is one of the most comprehensive analyses to date about plastic consumption by fish, a significant portion of the ocean has yet to be studied. This includes ocean gyres, where most plastic pollution ends up, as well as polar regions. Studying these difficult-to-access regions, said Savoca, will be important for filling gaps in our knowledge.

When used to treat a poisoning or overdose, activated charcoal is usually safe, but it needs to be administered only in a health care facility.

Side effects are more likely when it is used on a long-term basis to treat conditions like excess gas.

Side effects. When you take it by mouth, activated charcoal can cause:

In more serious cases, it can cause gastrointestinal blockages.

Risks. Do not combine activated charcoal with drugs used for constipation (cathartics such as sorbitol or magnesium citrate). This can cause electrolyte imbalances and other problems.

Interactions. Activated charcoal may reduce or prevent the absorption of certain drugs. This may include drugs such as:

Do not use activated charcoal as a supplement if you take these medications. Activated charcoal may also reduce absorption of certain nutrients.

The U.S. Food and Drug Administration (FDA) does regulate dietary supplements however, it treats them like foods rather than medications. Unlike drug manufacturers, the makers of supplements don’t have to show their products are safe or effective before selling them on the market.

Be sure to tell your doctor about any supplement you're taking, even if it's natural. That way, your doctor can check on any potential side effects or interactions with medications, foods, or other herbs and supplements. They can let you know if the supplement might increase your risks.


Natural Medicines Comprehensive Database: "Activated Charcoal."

Clinical Toxicology, 2005.

Eddelston, M. The Lancet. Feb. 16, 2008.

Neuvonen, P. Medical Toxicology and Adverse Drug Experience, January-December 1988.


Material der hier untersuchten Grabgänge, ursprünglich eingeführt als Eione moniliformis Tate, wurde aus heterolithischen Sandstein- und Siltstein-Schichten eines küstennahen Aufschlusses nahe der Stadt Howick (Northumberland, UK) geborgen. Diese wechsellagernden (“hummocky cross”)-Schichten gehören zur karbonischen Stainmore-Formation und repräsentieren marine Schelfablagerungen. Da der Name Eione schon früher verwendet worden ist um eine Gastropoden-Gattung zu beschreiben, handelt es sich bei Eione Tate um ein jüngeres Homonym von Eione Rafinesque. Aufgrund dieser Tatsache wurde zuvor eine neue Ichnogattung – Parataenidium Buckman – aufgestellt, die Gänge mit zwei eindeutigen Lagen umfasst und auch E. moniliformis inkludiert. Unter Verwendung von dreidimensionalen morphologischen Modellierungstechniken ist unsere Untersuchung darauf ausgerichtet: (1) den jetzigen taxonomischen Status von Parataenidium moniliformis zu klären, und (2) ein aktualisiertes Modell des Aufbaus zu liefern. Die Zuordnung von Eione moniliformis zu Parataenidium war problematisch insbesondere aufgrund der Tatsache, dass dieser nicht aus zwei eindeutigen Lagen sondern stattdessen aus verfüllten nierenförmigen Sedimenteinheiten aufgebaut ist. Diese wurden durch einen mehrstufigen Prozess gebildet, wobei der spurenerzeugende Organismus eine kleine offene Höhlung beibehalten hat, durch die Nahrung aufgenommen werden konnte. Dementsprechend wird hier die neue Ichnogattung Neoeione vorgeschlagen, um das ursprünglich von Tate beschriebene Material unterbringen zu können.