Category Zoology

When we bite and chew food, three sets of powerful muscles work together to move the lower jaw. As the muscles move the jaw up and down and from side to side, food is ground down by the molars in the back of the mouth.

Temporal muscle

Temporal muscle pulls the lower jaw up. Along with the medial pterygoid, lateral pterygoid and masseter muscles, it belongs to the group masticatory muscles. The temporalis muscle runs superficially, from the temporal bone to the coronoid process of mandible.

Pterygoid muscle

Pterygoid muscle pulls the hinge joint that opens the jaw. It belongs to the group of masticatory muscles, along with the lateral pterygoid, masseter and temporal muscles. 

Masseter muscle

The masseter muscle is a facial muscle that plays a major role in the chewing of solid foods. The muscle is shaped similar to a parallelogram, connecting to the mandible (lower jawbone) and the cheekbone. Masseter muscle closes the jaw with great force.

Jaw muscles

The chewing muscles, which are attached to the skull, can exert great force. The lower jaw can withstand this pressure because it is the strongest bone in the face.

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Incisor

The incisors are chisel shaped teeth located anteriorly within the oral cavity. Their name originates from the Latin word ‘incidere’, which means ‘to cut’. Hence, their main function is to cut food during mastication. The incisors are used for cutting and biting.

Canine

The canines tear and shred food. The first baby canines come in between the ages of 16 months and 20 months. The upper canines grow in first, followed by the lower canines.

Lower adult canines emerge in the opposite way. First, the lower canines poke through the gums around age 9, then the upper canines come in at age 11 or 12.

Root

The roots are normally buried in bone, and they serve to anchor the tooth in position. The roots are covered with a thin layer of bone, and they are inserted into sockets in the bone of the jaw. The long, pointed root anchors the tooth firmly in the jawbone.

Permanent tooth

The permanent teeth ate tucked up into the facial bones until they are ready to emerge. Permanent teeth can last a lifetime and it is very important to maintain them to prevent tooth decay developing and damaging them. Tooth decay can be prevented through brushing and flossing daily and attending regular dental checkups

Dentine

Dentine gives shape to the tooth and supports the enamel crown. Its strong, honeycomb structure helps the tooth withstand the powerful squashing force created by our jaws when we bite into food.

Parts of a tooth

The part of a tooth that you can see is the crown. It is coated in enamel – the hardest substance in the body. Beneath is a layer of bone-like tissue called dentine. The pulp cavity at the centre contains the tooth’s blood vessels and nerves.

Premolar

Premolar teeth are between the canine front teeth and the molars. These are transitional teeth; teeth that transition between the tearing function of the canines and the grinding function of the molars. Those grinding teeth only appear in the permanent set.

Molar

This is a permanent molar, which has recently emerged. Like premolars, these crush and grind food. Molars are designed to sustain great amounts of force from chewing, grinding, and clenching, and each molar is anchored to the jaw bone with two to four roots.

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The teeth start the process of digestion by breaking food down into pieces small enough to swallow. Teeth also give shape to the face and help us to pronounce sounds when we speak.

We grow two sets of teeth in our lifetime. The first set, the milk teeth, start to emerge from a baby’s gums at about six months or age. Then from six years, the second set of permanent teeth starts to emerge. At the same time, the roots of the milk teeth are absorbed by the body, so the teeth become loose and eventually fall out.

With the lips and tongue, teeth help form words by controlling airflow out of the mouth. The tongue strikes the teeth or the roof of the mouth as some sounds are made.

When we eat, our teeth tear, cut, and grind food in preparation for swallowing.

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When we eat, it’s important that food does not enter our airways and make us choke. So as we swallow, the body automatically closes off the airways in the throat and nose.  A flap of tissue called the epiglottis drops over the entrance to the windpipe. The soft palate lifts up to block access to the nasal cavity, too.

Chewing food

While we chew food, we can still breathe because the positions of the epiglottis and soft palate allow air in through the nose. As we prepare to swallow, the tongue pushes the food back into the throat.

Swallowing

As the food hits the back of the throat, it triggers a reflex action in the body. The soft palate rises to block the nasal cavity, while the epiglottis folds down to cover the windpipe. The food is directed safely down the oesophagus, towards the stomach.

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This section through a head shows the mouth, the oral cavity (Space inside the mouth), and throat. At the back of the throat are the tonsils, which help destroy harmful bacteria that are carried into the mouth with food or in the air. The tongue is not shown, so that the other organs can be seen more clearly.

Nasal cavity

The nose is an olfactory and respiratory organ. It consists of nasal skeleton, which houses the nasal cavity. Air is carried through this space between the nostrils and throat.

Nasopharynx

This is the upper part of the throat. It is a part of the pharynx, which comprises three separate segments: the nasopharynx, oropharynx, and the hypopharynx.

Soft palate

The soft palate is the muscular part at the back of the roof of the mouth. It sits behind the hard palate, which is the bony part of the roof of the mouth. This flap stops entering the nasal cavity while swallowing.

Hard palate

The hard palate is the horizontal bony plate that makes a subsection of the palate of the mouth. It makes the anterior two-thirds of the roof of the oral cavity. This bony plate forms most of the roof of the mouth.

Tonsils

The tonsils sit at the entrance to the throat. The tonsils are part of the lymphatic system, which helps to fight infections. However, removal of the tonsils does not seem to increase susceptibility to infection. Tonsils vary widely in size and swell in response to infection.

Oropharynx

The oropharynx forms part of the pharynx, being the continuation of the oral cavity and nasopharynx superiorly, and the larynx and hypopharynx inferiorly. The oropharynx is the middle part of the throat.

Epiglottis

The epiglottis is a leaf-shaped flap of cartilage located behind the tongue, at the top of the larynx, or voice box. This flap can fold back to stop food from entering the windpipe. The epiglottis also helps with some aspects of sound production in certain languages.

Larynx (voice box)

Sounds are made when air passes through the larynx. The larynx plays an essential role in human speech. During sound production, the vocal cords close together and vibrate as air expelled from the lungs passes between them. 

Windpipe (trachea)

The trachea, commonly known as the windpipe, is a tube about 4 inches long and less than an inch in diameter in most people. The trachea begins just under the larynx (voice box) and runs down behind the breastbone (sternum). The trachea then divides into two smaller tubes called bronchi: one bronchus for each lung. Sounds are made when air passes through the larynx.

Oesophagus

The oesophagus is a fibromuscular tube, approximately 25cm in length, that transports food from the pharynx to the stomach. This transports food from the throat to the stomach.

Saliva producer

Under the tongue are the sublingual glands, one of three pairs of saliva-producing (salivary) glands in the mouth. Saliva is the slimy substance that coats the mouth’s surface. It keeps the mouth moist and clean and makes chewing easier. It also contains anti-bacterial chemicals, and enzymes to break down food.

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The mouth is the gateway for food and drink to enter the body. It also helps to carry air in and out, and we shape the mouth to produce different sounds when we speak.

The mouth is bounded by the lips, the roof and flooe of the mouth, and the cheek muscles. It opens into the throat, a muscular tube that runs down the neck. Only air travels in the top section, which connects to the nose. Both air and food pass through the middle section, but not at the same time. The bottom section divides into two branches – the oesophagus, which carries food to the stomach, and the windpipe, which channels air to the lungs.

The mouth is an oval-shaped cavity inside the skull. The two main functions of the mouth are eating and speaking. Parts of the mouth include the lips, vestibule, mouth cavity, gums, teeth, hard and soft palate, tongue and salivary glands. The mouth is also known as the oral cavity or the buccal cavity.

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