clinical photography

Clinical photography (anatomy & physiology)

Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is generated over immediate and long timescales. Anatomy and physiology, which study the structure and function of organisms and their parts, make a natural pair of related disciplines, and they are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine

Anatomy is the study of the structure and relationship between body parts. Physiology is the study of the function of body parts and the body as a whole. Some specializations within each of these sciences follow: Gross (macroscopic) anatomy is the study of body parts visible to the naked eye, such as the heart or bones.

                                                                   Body cavities and membranes

In most cases, the body is described as having two main cavities called the “dorsal and ventral body cavities”. Some anatomical references do not recognize the dorsal body cavity but we will use it in this example because it’s used by many professionals and colleges.    

Dorsal body cavity

The dorsal body cavity protects organs of the nervous system and has two subdivisions. The cranial cavity is the area within the skull and encloses the brain. The spinal (vertebral) cavity encases the vertebral column and spinal cord.      

 Ventral Body cavity

Like the dorsal cavity, the ventral cavity has two subdivisions. The superior division is called the thoracic cavity. The thoracic cavity is surrounded by the ribs and muscles in the chest. It’s further subdivided into lateral pleural cavities (each pleural cavity envelopes a lung) and the mediastinum. Within The pericardial cavity lies within the mediastinum. It encloses the heart and remaining thoracic organs (trachea, oesophagus, etc.).

The inferior division of the ventral body cavity is called the “abdominopelvic cavity” and is separated from the thoracic cavity by the diaphragm. The abdominopelvic cavity is also separated into two subdivisions, the “abdominal cavity” and “pelvic cavity“. The abdominal cavity contains the stomach, spleen, liver, intestines, and a few other organs. The pelvic cavity (inferior) contains the urinary bladder, rectum, and some reproductive organs.

Membranes in the Ventral body cavity

The walls of the ventral body cavity and outer covering of its organs contain a thin covering called the serosa (also called serous membrane). It is a double-layered membrane made up of two parts called the “parietal serosa” (lines the cavity walls) and “visceral serosa” (covers organs in the cavity). The serous membranes are separated by a thin layer of fluid called “serous fluid“. Serous fluid is secreted by both membranes and acts as a lubricant, allowing organs to slide in the cavity without causing friction.

Typically, the serous membranes are named according to the cavity and organ they associate with. For instance, the parietal pericardium lines the pericardial cavity.        

Abdominopelvic regions and quadrants”

Because it’s so large, the abdominopelvic cavity is separated into regions and quadrants. The quadrants are self-explanatory and can be figured out easily by looking at the abdominopelvic cavity. They consist of the:

Right upper quadrant (RUQ)

Left upper quadrant (LUQ)

Right lower quadrant (RLQ)

Left lower quadrant (LLQ)

Simply draw a cross over the cavity separating it into four boxes, then use the directional terms accordingly.

Abdominopelvic Regions-The 9 regions of the abdominopelvic cavity

Umbilical region– centre-most region (belly button)

Epigastric region– superior to the umbilical region (above belly)

Hypogastric region– inferior to the umbilical region (pubic area)

Right and left iliac (inguinal region)-located lateral to the hypogastric region

Right and left lumbar regions– lateral to the umbilical region

Right and left hypochondriac regions– lateral to the epigastric region

Other body cavities

Nasal cavity– is part of the respiratory system. Located within the nose (and posterior).

Orbital cavities– house the eyes

Oral cavity– the mouth, contains the teeth and gums

Synovial cavities–  surround freely movable joints and secrete a lubricating fluid like serous membranes. 

The Salivary Glands

Several glands associated with the oral cavity secrete saliva.

Saliva:

-Cleanses the mouth

-Helps moisten and compact food into a round mass called a bolus

-Contains enzymes that begin the chemical breakdown of starch

-Dissolves food chemicals so they can be “tasted”

Most saliva is produced by major or extrinsic salivary glands that lie outside the oral cavity and empty their secretions into it. Minor or intrinsic salivary glands within the oral cavity alter the output slightly (note: extrinsic glands lie outside of oral cavity, intrinsic glands lie within oral cavity). The major salivary glands are paired and develop from the oral mucosa and stay connected to it by small ducts. The large, triangle shaped parotid gland (par=near, otid=ear) lies anterior to the ear between the skin and masseter muscle. Its main duct opens into the vestibule next to the second upper molar (view the green duct in image above).

Facial nerves run through the parotid gland to muscles in the face used for facial expression. For this reason, surgery on this gland is risky and could cause facial paralysis.

The submandibular, parotid, and sublingual salivary glands in association with the left side of oral cavity.

Mumps, a common disease amongst children, is an inflammation of the parotid glands caused by the mumps (myxovirus) virus. The virus spreads from person to person in saliva. If you view t

he parotid gland in the image above, you will see why people with mumps complain that hurts to chew. Other symptoms include fever and pain when swallowing acidic food or liquid (pickles, grapefruit). Mumps in adult males carries a 25% risk of infecting the testes, which can lead to sterility.

The submandibular gland is about the size of a walnut. Its duct runs underneath the mucosa in the oral cavity floor and opens underneath the tongue at the base of the lingual frenulum. The sublingual gland has a small, almond shape and lies in front of the submandibular gland under the tongue. It has 10-20 ducts which open into the floor of the mouth.

The salivary glands are composed of two types of secretory cells, serous and mucous. Serous cells produce a watery secretion containing ions, enzymes, and a small amount of mucin. Mucous cells produce mucus. The submandibular and parotid glands contain a large percentage of serous cells. The sublingual glands contain mostly mucous cells.

Composition of Saliva

Saliva is mainly water. In fact, it’s 97-99.5% water which makes it hypoosmotic. Its osmolarity depends on the glands that are active and the amount and type of stimulus for salivation. Generally, saliva is a bit acidic (6.75-7.00), but the PH can vary. Its solutes include electrolytes (mainly sodium, potassium, chloride, and bicarbonate); the digestive enzymes salivary amylase and lingual lipase; the proteins mucin, IgA, and lysozyme; metabolic wastes (uric acid, urea). When dissolved in water, the glycoprotein mucin forms thick mucus that lubricates the oral cavity and hydrates foodstuffs.

Saliva protects against microorganisms because it has:

IgA antibodies

Lysozyme- a bactericidal enzyme (it inhibits bacterial growth in the mouth and it’s unclear whether or not it may help prevent tooth decay

Defensins- defensins function as cytokines and call defensive cells (lymphocytes) into the mouth

Control of Salivation

The minor salivary glands secrete saliva continuously, keeping the mouth optimally moist. When food enters, the major glands activate and large amounts of saliva pour out. The average human being produces around 1500ml of saliva per day, but it can be a great deal higher if the glands are stimulated properly. For the most part, salivation is controlled by the parasympathetic division of the autonomic nervous system. When food is ingested, chemoreceptors and mechanoreceptors in the mouth send signals to the salivatory nuclei in the brain stem to the pons and medulla. As a result, parasympathetic nervous system activity increases. Impulses sent by motor fibres in the facial (VII) and glossopharyngeal (IX) nerves dramatically increase the output of watery saliva.

The chemoreceptors are activated the most by acidic foods and liquids (vinegar, pickles, etc). The mechanoreceptors are activated by almost any type of mechanical stimulus in the mouth (chewing)      

 Digestive system: The alimentary canal and accessory digestive organs

Organs of the digestive system are divided into two main groups: organs within the alimentary canal and accessory digestive organs.

The alimentary canal, which is also called the gastrointestinal (GI) tract or gut, is the entire length of tube that winds through the body from the mouth to the anus. It digests, breaks down and absorbs food through its lining into the blood.

Organs within the alimentary canal include the mouth, pharynx, oesophagus, stomach, small intestine, and large intestine. The alimentary canal is considered outside of the body because it is open to the external environment at each end (mouth, anus).

The accessory digestive organs include the tongue, teeth, gallbladder, salivary glands, liver, and pancreas. While the teeth and tongue lie within the mouth, the digestive glands and gallbladder lie outside of the GI tract and connect to it through pathways called ducts. The digestive glands aid in mechanical breakdown of food by producing several types of secretions.

The process of digestion involves six steps

1.       Ingestion– is the act of taking food into the digestive tract. In short, ingestion is eating.

2.       Propulsion– is the manner in which food is moved through the digest tract. This includes swallowing and peristalsis. Peristalsis is the main mean of propulsion and involves contraction and relaxation of muscles surrounding the organs. It’s main purpose is to squeeze food through the GI tract (a small amount of mixing occurs also). Peristalsis is so strong that you would continue to digest food even if you were upside down.

3.       Mechanical breakdown– includes chewing, mixing-food with the tongue, stomach churning, and segmentation (constrictions in the small intestine). Mechanical breakdown increases surface area which increases absorption. Segmentation mixes food with digestive juices in the small intestine which also increases absorption.

4.       Digestion– is the chemical breakdown of food. It involves a series of steps, but the main idea is that enzymes are secreted into the alimentary canal (GI tract) by accessory digestive glands and the gall bladder that aid in the breakdown of food molecules.

5.       Absorption- is the uptake of end products of digestion into the blood or lymph through the walls of the GI tract.

6.       Defecation– eliminates whatever is indigestible and not absorbed through the GI tract out of the body through the anus as feces.