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Stomach sagittal section

Stomach sagittal section


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Can anyone please tell me where is exactly the stomach in this image?

This is a sagittal section from the University of Michigan Visible Human Browsers.

Thank you.


The below structure circled in green clearly is part of the stomach antrum. The location is correct, and the mucosal folds are characteristic. Kerckring valves of the small intestine and semilunar folds of the colon both look different.


Stomach sagittal section - Biology

When an organism is in its standard anatomical position, positional descriptive terms are used to indicate regions and features.

Learning Objectives

Describe the standard position in human anatomy

Key Takeaways

Key Points

  • In standard anatomical position, the limbs are placed similarly to the supine position imposed on cadavers during autopsy.
  • The anatomical position of the skull is the Frankfurt plane. In this position, the lower margins of the orbitals (eye sockets), the lower margin of the orbits, and the upper margins of the ear canals (poria) lie in the same horizontal plane.
  • Because animals can change orientation with respect to their environments and appendages can change position with respect to the body, positional descriptive terms refer to the organism only in its standard anatomical position to prevent confusion.

Key Terms

  • appendage: A limb of the body.
  • supine: Lying on its back, reclined.
  • anatomical position: The standard position in which the body is standing with feet together, arms to the side, and head, eyes, and palms facing forward.

The Need for Standardization

Standard anatomical position is the body orientation used when describing an organism’s anatomy. Standardization is necessary to avoid confusion since most organisms can take on many different positions that may change the relative placement of organs. All descriptions refer to the organism in its standard anatomical position, even when the organism’s appendages are in another position. Thus, the standard anatomical position provides a “gold standard” when comparing the anatomy of different members of the same species.

Relative location in the anatomical position: Many terms are used to describe relative location on the body. Cranial refers to features closer to the head, while caudal refers to features closer to the feet. The front of the body is referred to as anterior or ventral, while the back is referred to as posterior or dorsal. Proximal and distal describe relative position on the limbs. Proximal refers to a feature that is closer to the torso, while distal refers to a feature that is closer to the fingers/toes. Medial and lateral refer to position relative to the midline, which is a vertical line drawn through the center of the forehead, down through the belly button to the floor. Medial indicates a feature is closer to this line, while lateral indicates features further from this line.

Standard Anatomical Position in Humans

The standard anatomical position is agreed upon by the international medical community. In this position, a person is standing upright with the lower limbs together or slightly apart, feet flat on the floor and facing forward, upper limbs at the sides with the palms facing forward and thumbs pointing away from the body, and head and eyes directed straight ahead. In addition, the arms are usually placed slightly apart from the body so that the hands do not touch the sides. The positions of the limbs, particularly the arms, have important implications for directional terms in those appendages.

The basis for the standard anatomical position in humans comes from the supine position used for examining human cadavers during autopsies. Dissection of cadavers was one of the primary ways humans learned about anatomy throughout history, which has tremendously influenced the ways by which anatomical knowledge has developed into the scientific field of today.

Standard anatomical position: The regions of the body in standard anatomical position, in which the body is erect.

In humans, the standard anatomical position of the skull is called the Frankfurt plane. In this position, the orbitales (eye sockets), lower margins of the orbits, and the poria (ear canal upper margins) all lie in the same horizontal plane. This orientation represents the position of the skull if the subject were standing upright and looking straight ahead.

It is important to note that all anatomical descriptions are based on the standard anatomical position unless otherwise stated.


Chapter 1 The Human Body: An Orientation (Mastering A&P)

What does the principle of complementarity of structure and function mean?

A. All structures perform the same functions.
B. The age of the structure determines the function it performs.
C. Functions are determined by environmental conditions, not by structure.
D. Function reflects structure and structure determines function.

Which organ systems function as control systems, communicating with other cells/organs to regulate their activities?

A. nervous and endocrine systems
B. nervous and cardiovascular systems
C. cardiovascular and endocrine systems
D. cardiovascular and digestive systems

Which materials are exchanged between blood and cells, as depicted by the set of arrows labeled 5 in the above figure?

A. waste products
B. oxygen
C. carbon dioxide
D. nutrients
E. all of the listed responses are correct

Which of the following represents the correct order in which the components interact in a homeostatic control system?

A. the variable, the receptor, and the set point
B. the effector, the stimulus, and the receptor
C. the receptor, the control center, and the effector
D. the receptor, the stimulus, and the effector

Which of the following is true of negative feedback mechanisms?

A. The variable deviates farther and farther from its normal range.
B. They are used for processes such as blood clotting and labor contractions.
C. The effect or response enhances the original stimulus.
D. The effect opposes the original stimulus or reduces its intensity.

Which of the following is true of negative feedback mechanisms?

A. sagittal
B. lateral
C. transverse
D. coronal

Which of the following statements is correct?

A. The umbilicus is medial to the chin.
B. The umbilicus is caudal to the chin.
C. The chin is caudal to the umbilicus.
D. The umbilicus is superior to the chin.

Which of the following can be described as a cut made diagonally between the horizontal and the vertical planes?

A. transverse section
B. cross section
C. sagittal section
D. oblique section

What is the function of serous fluid?

A. It aids in the repair of damaged organs.
B. It helps the stomach and other organs maintain neutral buoyancy within body cavities, even during fluctuations in atmospheric pressure, or when gases, such as oxygen or methane, are present in varying ratios.
C. It enables organs, such as the heart and the stomach, to slide across cavity walls and each other without friction.
D. It prevents the organs from drying out when in contact with air.

Which of the following is NOT one of the subdivisions of anatomy?

A. developmental anatomy
B. systemic anatomy
C. gross anatomy
D. renal anatomy

Which of the following best defines anatomy?

A. It is the study of tissues.
B. It is the study of all chemical reactions that occur within body cells.
C. It is the study of how the body parts work and carry out their life-sustaining activities.
D. It is the study of the structure of body parts and their relationships to one another.

What level of structural organization is represented by the image numbered 5 in the figure?


Other animals

The stomachs of some other animals differ considerably from that of humans many have multiple-chambered organs or special adaptations. The stomachs of cows and most cud-chewing (ruminant) animals are divided into four separate parts. Food is received first in the rumen, where mucus is added and cellulose is broken down. Next, it goes back to the mouth to be thoroughly rechewed. When swallowed again, it is passed to the second and third chambers, the reticulum and omasum, where water is extracted and absorbed. The food then goes to a final chamber, the abomasum, to receive the digestive enzymes.

Birds have a three-chambered stomach: the first chamber, the crop, receives the food initially and either stores or begins to moisten and soften (macerate) it the true stomach area adds digestive juices and the gizzard, with its stones, or toothlike structures, grinds the food.

Rodents have only one stomach area, and many must eat their food twice before absorption takes place. Food is eaten and passed through the lower digestive tract, where it is coated with metabolites to help break it down. The fecal material is then re-eaten and mixed with additional food. Enzymes and water are removed from the once-passed material by the stomach and used to help digest new nutritional substances. Dry fecal pellets are finally excreted.

The starfish can turn its stomach inside out and extrude it partly from the body to eat the soft contents of shelled animals such as clams. Camels and llamas can regurgitate their stomach contents and spit this material at approaching enemies. Crayfish produce stones of calcium salts in their stomach. These are stored until the animal sheds its external shell, when the stones are reabsorbed by the stomach and used in forming a new shell.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Adam Augustyn, Managing Editor, Reference Content.


Picture of the Abdomen

The abdomen (commonly called the belly) is the body space between the thorax (chest) and pelvis. The diaphragm forms the upper surface of the abdomen. At the level of the pelvic bones, the abdomen ends and the pelvis begins.

The abdomen contains all the digestive organs, including the stomach, small and large intestines, pancreas, liver, and gallbladder. These organs are held together loosely by connecting tissues (mesentery) that allow them to expand and to slide against each other. The abdomen also contains the kidneys and spleen.

Many important blood vessels travel through the abdomen, including the aorta, inferior vena cava, and dozens of their smaller branches. In the front, the abdomen is protected by a thin, tough layer of tissue called fascia. In front of the fascia are the abdominal muscles and skin. In the rear of the abdomen are the back muscles and spine.


Anatomical Terminology

Anatomists and health care providers use terminology that can be bewildering to the uninitiated. However, the purpose of this language is not to confuse, but rather to increase precision and reduce medical errors. For example, is a scar “above the wrist” located on the forearm two or three inches away from the hand? Or is it at the base of the hand? Is it on the palm-side or back-side? By using precise anatomical terminology, we eliminate ambiguity. Anatomical terms derive from ancient Greek and Latin words. Because these languages are no longer used in everyday conversation, the meaning of their words does not change.

Anatomical terms are made up of roots, prefixes, and suffixes. The root of a term often refers to an organ, tissue, or condition, whereas the prefix or suffix often describes the root. For example, in the disorder hypertension, the prefix “hyper-” means “high” or “over,” and the root word “tension” refers to pressure, so the word “hypertension” refers to abnormally high blood pressure.

Anatomical Position

To further increase precision, anatomists standardize the way in which they view the body. Just as maps are normally oriented with north at the top, the standard body “map,” or anatomical position , is that of the body standing upright, with the feet at shoulder width and parallel, toes forward. The upper limbs are held out to each side, and the palms of the hands face forward as illustrated in (Figure). Using this standard position reduces confusion. It does not matter how the body being described is oriented, the terms are used as if it is in anatomical position. For example, a scar in the “anterior (front) carpal (wrist) region” would be present on the palm side of the wrist. The term “anterior” would be used even if the hand were palm down on a table.

A body that is lying down is described as either prone or supine. Prone describes a face-down orientation, and supine describes a face up orientation. These terms are sometimes used in describing the position of the body during specific physical examinations or surgical procedures.

Regional Terms

The human body’s numerous regions have specific terms to help increase precision (see (Figure)). Notice that the term “brachium” or “arm” is reserved for the “upper arm” and “antebrachium” or “forearm” is used rather than “lower arm.” Similarly, “femur” or “thigh” is correct, and “leg” or “crus” is reserved for the portion of the lower limb between the knee and the ankle. You will be able to describe the body’s regions using the terms from the figure.

Directional Terms

Certain directional anatomical terms appear throughout this and any other anatomy textbook ((Figure)). These terms are essential for describing the relative locations of different body structures. For instance, an anatomist might describe one band of tissue as “inferior to” another or a physician might describe a tumor as “superficial to” a deeper body structure. Commit these terms to memory to avoid confusion when you are studying or describing the locations of particular body parts.

  • Anterior (or ventral ) Describes the front or direction toward the front of the body. The toes are anterior to the foot.
  • Posterior (or dorsal ) Describes the back or direction toward the back of the body. The popliteus is posterior to the patella.
  • Superior (or cranial ) describes a position above or higher than another part of the body proper. The orbits are superior to the oris.
  • Inferior (or caudal ) describes a position below or lower than another part of the body proper near or toward the tail (in humans, the coccyx, or lowest part of the spinal column). The pelvis is inferior to the abdomen.
  • Lateral describes the side or direction toward the side of the body. The thumb (pollex) is lateral to the digits.
  • Medial describes the middle or direction toward the middle of the body. The hallux is the medial toe.
  • Proximal describes a position in a limb that is nearer to the point of attachment or the trunk of the body. The brachium is proximal to the antebrachium.
  • Distal describes a position in a limb that is farther from the point of attachment or the trunk of the body. The crus is distal to the femur.
  • Superficial describes a position closer to the surface of the body. The skin is superficial to the bones.
  • Deep describes a position farther from the surface of the body. The brain is deep to the skull.

Body Planes

A section is a two-dimensional surface of a three-dimensional structure that has been cut. Modern medical imaging devices enable clinicians to obtain “virtual sections” of living bodies. We call these scans. Body sections and scans can be correctly interpreted, however, only if the viewer understands the plane along which the section was made. A plane is an imaginary two-dimensional surface that passes through the body. There are three planes commonly referred to in anatomy and medicine, as illustrated in (Figure).

  • The sagittal plane is the plane that divides the body or an organ vertically into right and left sides. If this vertical plane runs directly down the middle of the body, it is called the midsagittal or median plane. If it divides the body into unequal right and left sides, it is called a parasagittal plane or less commonly a longitudinal section.
  • The frontal plane is the plane that divides the body or an organ into an anterior (front) portion and a posterior (rear) portion. The frontal plane is often referred to as a coronal plane. (“Corona” is Latin for “crown.”)
  • The transverse plane is the plane that divides the body or organ horizontally into upper and lower portions. Transverse planes produce images referred to as cross sections.

Body Cavities and Serous Membranes

The body maintains its internal organization by means of membranes, sheaths, and other structures that separate compartments. The dorsal (posterior) cavity and the ventral (anterior) cavity are the largest body compartments ((Figure)). These cavities contain and protect delicate internal organs, and the ventral cavity allows for significant changes in the size and shape of the organs as they perform their functions. The lungs, heart, stomach, and intestines, for example, can expand and contract without distorting other tissues or disrupting the activity of nearby organs.

Subdivisions of the Posterior (Dorsal) and Anterior (Ventral) Cavities

The posterior (dorsal) and anterior (ventral) cavities are each subdivided into smaller cavities. In the posterior (dorsal) cavity, the cranial cavity houses the brain, and the spinal cavity (or vertebral cavity) encloses the spinal cord. Just as the brain and spinal cord make up a continuous, uninterrupted structure, the cranial and spinal cavities that house them are also continuous. The brain and spinal cord are protected by the bones of the skull and vertebral column and by cerebrospinal fluid, a colorless fluid produced by the brain, which cushions the brain and spinal cord within the posterior (dorsal) cavity.

The anterior (ventral) cavity has two main subdivisions: the thoracic cavity and the abdominopelvic cavity (see (Figure)). The thoracic cavity is the more superior subdivision of the anterior cavity, and it is enclosed by the rib cage. The thoracic cavity contains the lungs and the heart, which is located in the mediastinum. The diaphragm forms the floor of the thoracic cavity and separates it from the more inferior abdominopelvic cavity. The abdominopelvic cavity is the largest cavity in the body. Although no membrane physically divides the abdominopelvic cavity, it can be useful to distinguish between the abdominal cavity, the division that houses the digestive organs, and the pelvic cavity, the division that houses the organs of reproduction.

Abdominal Regions and Quadrants

To promote clear communication, for instance about the location of a patient’s abdominal pain or a suspicious mass, health care providers typically divide up the cavity into either nine regions or four quadrants ((Figure)).

The more detailed regional approach subdivides the cavity with one horizontal line immediately inferior to the ribs and one immediately superior to the pelvis, and two vertical lines drawn as if dropped from the midpoint of each clavicle (collarbone). There are nine resulting regions. The simpler quadrants approach, which is more commonly used in medicine, subdivides the cavity with one horizontal and one vertical line that intersect at the patient’s umbilicus (navel).

Membranes of the Anterior (Ventral) Body Cavity

A serous membrane (also referred to a serosa) is one of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities. The parietal layers of the membranes line the walls of the body cavity (pariet- refers to a cavity wall). The visceral layer of the membrane covers the organs (the viscera). Between the parietal and visceral layers is a very thin, fluid-filled serous space, or cavity ((Figure)).

There are three serous cavities and their associated membranes. The pleura is the serous membrane that encloses the pleural cavity the pleural cavity surrounds the lungs. The pericardium is the serous membrane that encloses the pericardial cavity the pericardial cavity surrounds the heart. The peritoneum is the serous membrane that encloses the peritoneal cavity the peritoneal cavity surrounds several organs in the abdominopelvic cavity. The serous membranes form fluid-filled sacs, or cavities, that are meant to cushion and reduce friction on internal organs when they move, such as when the lungs inflate or the heart beats. Both the parietal and visceral serosa secrete the thin, slippery serous fluid located within the serous cavities. The pleural cavity reduces friction between the lungs and the body wall. Likewise, the pericardial cavity reduces friction between the heart and the wall of the pericardium. The peritoneal cavity reduces friction between the abdominal and pelvic organs and the body wall. Therefore, serous membranes provide additional protection to the viscera they enclose by reducing friction that could lead to inflammation of the organs.

Chapter Review

Ancient Greek and Latin words are used to build anatomical terms. A standard reference position for mapping the body’s structures is the normal anatomical position. Regions of the body are identified using terms such as “occipital” that are more precise than common words and phrases such as “the back of the head.” Directional terms such as anterior and posterior are essential for accurately describing the relative locations of body structures. Images of the body’s interior commonly align along one of three planes: the sagittal, frontal, or transverse. The body’s organs are organized in one of two main cavities—dorsal (also referred to posterior) and ventral (also referred to anterior)—which are further sub-divided according to the structures present in each area. The serous membranes have two layers—parietal and visceral—surrounding a fluid filled space. Serous membranes cover the lungs (pleural serosa), heart (pericardial serosa), and some abdominopelvic organs (peritoneal serosa).

Review Chapter

What is the position of the body when it is in the “normal anatomical position?”

  1. The person is prone with upper limbs, including palms, touching sides and lower limbs touching at sides.
  2. The person is standing facing the observer, with upper limbs extended out at a ninety-degree angle from the torso and lower limbs in a wide stance with feet pointing laterally
  3. The person is supine with upper limbs, including palms, touching sides and lower limbs touching at sides.
  4. None of the above

To make a banana split, you halve a banana into two long, thin, right and left sides along the ________.

  1. coronal plane
  2. longitudinal plane
  3. midsagittal plane
  4. transverse plane

The lumbar region is ________.

  1. inferior to the gluteal region
  2. inferior to the umbilical region
  3. superior to the cervical region
  4. superior to the popliteal region

The heart is within the ________.

  1. cranial cavity
  2. mediastinum
  3. posterior (dorsal) cavity
  4. All of the above

Critical Thinking Question

In which direction would an MRI scanner move to produce sequential images of the body in the frontal plane, and in which direction would an MRI scanner move to produce sequential images of the body in the sagittal plane?

If the body were supine or prone, the MRI scanner would move from top to bottom to produce frontal sections, which would divide the body into anterior and posterior portions, as in “cutting” a deck of cards. Again, if the body were supine or prone, to produce sagittal sections, the scanner would move from left to right or from right to left to divide the body lengthwise into left and right portions.

If a bullet were to penetrate a lung, which three anterior thoracic body cavities would it enter, and which layer of the serous membrane would it encounter first?

The bullet would enter the ventral, thoracic, and pleural cavities, and it would encounter the parietal layer of serous membrane first.

Glossary


Serosa

Gastric serosa is the outermost layer of the stomach wall. It consists of a layer of simple squamous epithelium, known as mesothelium, and a thin layer of underlying connective tissue. The mesothelium produces serous fluid, which lubricates the outer wall of the stomach and ensures its smooth movement in the abdominal cavity. The serosa is continuous with the parietal peritoneum. It is absent at the attachment sites of the greater and lesser omenta to the stomach, as well as over a small superoposterior area near the cardiac orifice where the stomach is attached to the diaphragm via gastrophrenic and gastropancreatic folds.

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Complete Abdomen

If liver edge is edematous, try to measure free GB wall.

  • Take cine through GB if there is any abnormality (stones, polyp, adenomyomatosis).
  • Transverse and sagittal image of Gallbladder with patient LLD position to check for stones/ polyps and mobility.
  • Please document in report if there was a positive Murphy’s sign.
  • Sagittal image of right kidney in medial, middle and lateral views.
  • Sagittal measurement of right kidney. Take cine only if abnormality is present.
  • Transverse images of superior/mid/inferior right kidney.
  • Sagittal image of left kidney in medial, middle and lateral views.
  • Sagittal measurement of left kidney.
  • Transverse images of superior/mid/inferior left kidney.
  • Sagittal and transverse images through spleen with splenic length.
  • Sagittal image through left hemidiaphragm and spleen to assess for pleural effusions and ringdown.
  • Sagittal image through spleen and left kidney.
  • Sagittal and transverse image through midline and urinary bladder.
  • Document RLQ and LLQ (to check for ascites).
  • If a patient is coming in for pain, please document within the indication section or the “other” section what the current status of pain is. For instance, how long the patient has had pain, if it’s getting worse or better, and where exactly the pain is. Always take an image where the patient is hurting the most (label as “area of pain”). If this area is located where bowel is, take an image of the area with a linear transducer. When describing the pain, write “per patient, …” in the indication. Example: Per the patient, his pain is now in the RLQ and getting worse.
  • Cine clip of any abnormality or area of interest.
  • See Abdomen Doppler protocol for all Abdomen Doppler exams.
  • Say “Not well seen” if structure is not well seen.
  • Any masses, cysts, stones or abnormalities should be measured in three dimensions and have a 2D picture and a color image documented.

© 2021 Body Imaging Section | Site Setup: Martin Gunn | University of Washington | Seattle, WA


Contents

There could be any number of sagittal planes however, there is only one cardinal sagittal plane. The term cardinal refers to the one plane that divides the body into equal segments, with exactly one half of the body on either side of the cardinal plane. The term cardinal plane appears in some texts as the principal plane. The terms are interchangeable. [1]

The following terms are defined in reference to the anatomical model being in the upright orientation (standing):

  • A transverse (also known as axial or horizontal) plane is parallel to the ground in humans it separates the superior from the inferior, or put another way, the head from the feet.
  • A coronal (also known as frontal) plane is perpendicular to the ground in humans it separates the anterior from the posterior, the front from the back, the ventral from the dorsal.
  • A sagittal (also known as anteroposterior) plane is perpendicular to the ground, separating left from right. The midsagittal plane is the specific sagittal plane that is exactly in the middle of the body.
    • The midsagittal or median plane is in the midline i.e. it would pass through midline structures such as the navel or spine, and all other sagittal planes (also referred to as parasagittal planes) are parallel to it. Median can also refer to the midsagittal plane of other structures, such as a digit.

    The axes and the sagittal plane are the same for bipeds and quadrupeds, but the orientation of the coronal and transverse planes switch. The axes on particular pieces of equipment may or may not correspond to axes of the body, especially since the body and the equipment may be in different relative orientations.

    Brain viewed from below. This is an example of a transverse plane.

    Brain cut in half through the midsection. This is an example of a sagittal plane.

    Motion Edit

    When describing anatomical motion, these planes describe the axis along which an action is performed. So by moving through the transverse plane, movement travels from head to toe. For example, if a person jumped directly up and then down, their body would be moving through the transverse plane in the coronal and sagittal planes.

    A longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.

    Medical imaging Edit

    Sometimes the orientation of certain planes needs to be distinguished, for instance in medical imaging techniques such as sonography, CT scans, MRI scans, or PET scans. There are a variety of different standardized coordinate systems. For the DICOM format, the one imagines a human in the anatomical position, and an X-Y-Z coordinate system with the x-axis going from front to back, the y-axis going from right to left, and the z-axis going from toe to head. The right-hand rule applies. [2]

    Finding anatomical landmarks Edit

    In humans, reference may take origin from superficial anatomy, made to anatomical landmarks that are on the skin or visible underneath. As with planes, lines and points are imaginary. Examples include:

    • The midaxillary line, a line running vertically down the surface of the body passing through the apex of the axilla (armpit). Parallel are the anterior axillary line, which passes through the anterior axillary skinfold, and the posterior axillary line, which passes through the posterior axillary skinfold.
    • The mid-clavicular line, a line running vertically down the surface of the body passing through the midpoint of the clavicle.

    In addition, reference may be made to structures at specific levels of the spine (e.g. the 4th cervical vertebra, abbreviated "C4"), or the rib cage (e.g., the 5th intercostal space).

    Occasionally, in medicine, abdominal organs may be described with reference to the trans-pyloric plane, which is a transverse plane passing through the pylorus.

    Comparative embryology Edit

    In discussing the neuroanatomy of animals, particularly rodents used in neuroscience research, a simplistic convention has been to name the sections of the brain according to the homologous human sections. Hence, what is technically a transverse (orthogonal) section with respect to the body length axis of a rat (dividing anterior from posterior) may often be referred to in rat neuroanatomical coordinates as a coronal section, and likewise a coronal section with respect to the body (i.e. dividing ventral from dorsal) in a rat brain is referred to as transverse. This preserves the comparison with the human brain, whose length axis in rough approximation is rotated with respect to the body axis by 90 degrees in the ventral direction. It implies that the planes of the brain are not necessarily the same as those of the body.

    However, the situation is more complex, since comparative embryology shows that the length axis of the neural tube (the primordium of the brain) has three internal bending points, namely two ventral bendings at the cervical and cephalic flexures (cervical flexure roughly between the medulla oblongata and the spinal cord, and cephalic flexure between the diencephalon and the midbrain), and a dorsal (pontine or rhombic flexure) at the midst of the hindbrain, behind the cerebellum. The latter flexure mainly appears in mammals and sauropsids (reptiles and birds), whereas the other two, and principally the cephalic flexure, appear in all vertebrates (the sum of the cervical and cephalic ventral flexures is the cause of the 90 degree angle mentioned above in humans between body axis and brain axis). This more realistic concept of the longitudinal structure of vertebrate brains implies that any section plane, except the sagittal plane, will intersect variably different parts of the same brain as the section series proceeds across it (relativity of actual sections with regard to topological morphological status in the ideal unbent neural tube). Any precise description of a brain section plane therefore has to make reference to the anteroposterior part of the brain to which the description refers (e.g., transverse to the midbrain, or horizontal to the diencephalon). A necessary note of caution is that modern embryologic orthodoxy indicates that the brain's true length axis finishes rostrally somewhere in the hypothalamus where basal and alar zones interconnect from left to right across the median line therefore, the axis does not enter the telencephalic area, although various authors, both recent and classic, have assumed a telencephalic end of the axis. The causal argument for this lies in the end of the axial mesoderm -mainly the notochord, but also the prechordal plate- under the hypothalamus. Early inductive effects of the axial mesoderm upon the overlying neural ectoderm is the mechanism that establishes the length dimension upon the brain primordium, jointly with establishing what is ventral in the brain (close to the axial mesoderm) in contrast with what is dorsal (distant from the axial mesoderm). Apart from the lack of a causal argument for introducing the axis in the telencephalon, there is the obvious difficulty that there is a pair of telencephalic vesicles, so that a bifid axis is actually implied in these outdated versions.

    Some of these terms come from Latin. Sagittal means "like an arrow", a reference to the position of the spine that naturally divides the body into right and left equal halves, the exact meaning of the term "midsagittal", or to the shape of the sagittal suture, which defines the sagittal plane and is shaped like an arrow.


    Gastric Motility: Filling and Emptying

    Contractions of gastric smooth muscle serve two basic functions. First, it allows the stomach to grind, crush and mix ingested food, liquefying it to form what is called "chyme." Second, it forces the chyme through the pyloric canal, into the small intestine, a process called gastric emptying. The stomach can be divided into two regions on the basis of motility pattern: an accordion-like reservoir that applies constant pressure on the lumen and a highly contractile grinder.

    The proximal stomach, composed of the fundus and upper body, shows low frequency, sustained contractions that are responsible for generating a basal pressure within the stomach. Importantly, these tonic contractions also generate a pressure gradient from the stomach to the small intestine and are thus responsible for gastric emptying. Interestingly, swallowing of food and consequent gastric distention inhibits contraction of this region of the stomach, allowing it to balloon out and form a large reservoir without a significant increase in pressure—this phenomenon is called "adaptive relaxation."

    The distal stomach, composed of the lower body and antrum, develops strong peristaltic waves of contraction that increase in amplitude as they propagate toward the pylorus. These powerful contractions constitute a very effective gastric grinder they occur about 3 times per minute in people and 5 to 6 times per minute in dogs. There is a pacemaker in the smooth muscle of the greater curvature that generates rhythmic slow waves from which action potentials and hence peristaltic contractions propagate. As you might expect and at times hope, gastric distention strongly stimulates this type of contraction, accelerating liquefaction and hence, gastric emptying. The pylorus is functionally part of this region of the stomach—when the peristaltic contraction reaches the pylorus, its lumen is effectively obliterated—chyme is thus delivered to the small intestine in spurts.

    Motility in both the proximal and distal regions of the stomach is controlled by a very complex set of neural and hormonal signals. Nervous control originates from the enteric nervous system as well as parasympathetic (predominantly vagus nerve) and sympathetic systems. A large battery of hormones have been shown to influence gastric motility—for example, both gastrin and cholecystokinin act to relax the proximal stomach and enhance contractions in the distal stomach. The bottom line is that the patterns of gastric motility likely are a result of smooth muscle cells integrating a large number of inhibitory and stimulatory signals.

    Liquids readily pass through the pylorus in spurts, but solids must be reduced to a diameter of less than 1-2 mm before passing the pyloric gatekeeper. Larger solids are propelled by peristalsis toward the pylorus, but then refluxed backward when they fail to pass through the pylorus - this continues until they are reduced in size sufficiently to flow through the pylorus.

    At this point, you may be asking "What happens to solids that are indigestible - for example, a rock or a penny? Will it remain forever in the stomach?" If the indigestible solids are large enough, they indeed cannot pass into the small intestine and will either remain in the stomach for long periods, induce a gastric obstruction or, as every cat owner knows, be evacuated by vomition. However, many of the indigestible solids that fail to pass through the pylorus shortly after a meal do pass into the small intestine during periods between meals. This is due to a different pattern of motor activity called the migrating motor complex, a pattern of smooth muscle contractions that originates in the stomach, propagates through the intestines and serves a housekeeping function to periodically sweep out the gastrointestinal tract.


    Watch the video: Sectional anatomy of the abdomen and pelvis - sagittal sections (December 2022).