Changes

==Oral Cavity==

==Oral Cavity==

===Teeth===

===[[Teeth - Anatomy & Physiology|Teeth]]===

[[Image:Horse teeth.jpg|thumb|right|200px|Tooth identifation in the horse- copyright Academy of Equine Dentistry-2008]]

[[Image:Horse teeth.jpg|thumb|right|200px|Tooth identifation in the horse - © Academy of Equine Dentistry-2008]]

====Dental Formula====

====Dental Formula====

====Molars====

====Molars====

[[Image:Horse Tooth.jpg|thumb|right|200px|Horse tooth - Copyright Malcom Morley]]

[[Image:Horse Tooth.jpg|thumb|right|200px|Horse tooth - © Malcom Morley]]

The molars have enlarged surfaces and higher [[Enamel Organ#Crown|crowns]]. They have delayed [[Enamel Organ#Root|root]] development and complicated folding of [[Enamel Organ#Enamel|enamel]].

The molars have enlarged surfaces and higher [[Enamel Organ#Crown|crowns]]. They have delayed [[Enamel Organ#Root|root]] development and complicated folding of [[Enamel Organ#Enamel|enamel]].

====Ageing====

====Ageing====

Horses can be aged by their teeth. At 2 and a half the first permanent incisor will erupt; At 3 and a half the second permanent incisor will erupt and at 4 and a half the third permanent incisor will erupt. Over 5 years of age the folding of the enamel ring ('''infundibulum''') can indicate age. There is a 7 year hook and over 13 years of age a '''dental star''' will be present.

Horses can be aged by their teeth. At two and a half years of age the first permanent incisor will erupt; at three and a half the second permanent incisor will erupt and at four and a half the third permanent incisor will erupt. Over five years of age the folding of the enamel ring ('''infundibulum''') can indicate age. There is a seven year hook and over 13 years of age a '''dental star''' will be present.

The '''Galvayne's Groove''' is a brown groove on the upper corner incisor teeth and indicates that the horse is over 10 years old. At 15 the groove will be approximately half way down the tooth; At 20 the groove will run down the whole tooth; Over 20 the grove begins to disappear; At 25 the groove will only be visible on the bottom half of the tooth. At 30 the groove will usually be gone.

The '''Galvayne's Groove''' is a brown groove on the upper corner incisor teeth and indicates that the horse is over 10 years old. At 15 the groove will be approximately half way down the tooth; At 20 the groove will run down the whole tooth; Over 20 the grove begins to disappear; At 25 the groove will only be visible on the bottom half of the tooth. At 30 the groove will usually be gone.

===Palate===

===Palate===

There is a tight laryngeal cuff around the laryngeal entrance, therefore the soft palate cannot be raised for long periods of time; and thus horses are obligate nasal breathers. Laryngeal cuffing prevents [[Vomiting|vomiting]].

Horses have a tight laryngeal cuff around the laryngeal entrance, therefore the [[Soft Palate|soft palate]] cannot be raised for long periods of time. This causes them to be obligate nasal breathers. Laryngeal cuffing also prevents [[Vomiting|vomiting]]. There are no specific species diferences in the [[Hard Palate|hard palate]].

==Oesophagus==

==[[Oesophagus - Anatomy & Physiology|Oesophagus]]==

In the horse, the oesophageal lumen narrows at the thoracic inlet and oesophageal hiatus of the diagphragm; this predisposes them to impaction (choke). Another species difference is that striated muscle exists only in the rostral 65% of the oesophagus.

In the horse, the oesophageal lumen narrows at the thoracic inlet and oesophageal hiatus of the diaphragm; this predisposes them to impaction (choke). Another factor specific to horses is that striated muscle exists only in the rostral 65% of the oesophagus.

==Stomach==

==Stomach==

[[Image:Margo Plicatus.jpg|thumb|right|250px|Equine Stomach with Margo Plicatus - Copyright RVC 2008]]

[[Image:Margo Plicatus.jpg|thumb|right|250px|Equine Stomach with Margo Plicatus - © RVC 2008]]

The horse has a [[Monogastric Stomach - Anatomy & Physiology|monogastric stomach]] located on the left side of the abdomen. A region called the '''margo plicatus''' is present which separates the glandular and non-glandular parts of the equine stomach. The non-glandular area is lined with squamous epithelium (not columnar).

The horse has a [[Monogastric Stomach - Anatomy & Physiology|monogastric stomach]] located on the left side of the abdomen. A region called the '''margo plicatus''' is present which separates the glandular and non-glandular parts of the equine stomach. The non-glandular area is lined with squamous epithelium (not columnar).

The stomach is relatively small (10% GIT) and its capacity is 8-16 litres. The equine stomach is rarely empty, retention time is short and expulsion into the [[Duodenum - Anatomy & Physiology|duodenum]] stops when feeding stops. Although fluid exits quickly, feed particles can be retained for more than 48 hours as digestion is initiated in the stomach. A 500kg horse can produce 30 litres of gastric juice in 24 hours. The strong '''cardiac sphincter''' allows movement of gas and fluid into the stomach, but not out of it. This prevents the animal from [[Vomiting|vomiting]]. Therefore, any disorder that results in aboral fluid movement from the small intestine results in fluid accumulation in the stomach (gastric reflux), dilation and eventually gastric rupture if left untreated.

The stomach is relatively small (10% GIT) and its capacity is 8-16 litres. The equine stomach is rarely empty, retention time is short and expulsion into the [[Duodenum - Anatomy & Physiology|duodenum]] stops when feeding stops. Although fluid exits quickly, feed particles can be retained for more than 48 hours as digestion is initiated in the stomach. A 500kg horse can produce 30 litres of gastric juice in 24 hours. The strong '''cardiac sphincter''' allows movement of gas and fluid into the stomach, but not out of it. This prevents the animal from [[Vomiting|vomiting]]. Therefore, any disorder that results in aboral fluid movement from the small intestine results in fluid accumulation in the stomach (gastric reflux), [[Gastric Dilation and Rupture - Horse|dilation and eventually gastric rupture]] if left untreated.

==Small Intestine==

==Small Intestine==