Changes

===Horns===

===Horns===

Horns have a central, conical bony core or '''corunal process''' that grows out from the [[Skull and Facial Muscles - Anatomy & Physiology#Frontal Bone|frontal bone]] of the skull.  After 6 months of age, the bone becomes hollow and the space within it is continuous with the [[Paranasal Sinuses - Anatomy & Physiology|frontal sinuses]].  The surface of the bone is ridged and porous and is covered with papillated [[Skin - Anatomy & Physiology#dermis|dermis]] that is continuous with the periosteum and [[Skin - Anatomy & Physiology#epidermis|epidermis]] which keratinises and forms the protective covering of the horn.  The substance of the horn is similar to that of the [[Hoof - Anatomy & Physiology|hoof]] and is a mixture of tubules and intertubular horn.  The new horn produced at the base is soft and often transparent and resembles the [[Hoof - Anatomy & Physiology|periople]] of the hoof, giving the horn a glossy appearance.

Horns have a central, conical bony core or '''cornual process''' that grows out from the [[Skull and Facial Muscles - Anatomy & Physiology#Frontal Bone|frontal bone]] of the skull.  After 6 months of age, the bone becomes hollow and the space within it is continuous with the [[Paranasal Sinuses - Anatomy & Physiology|frontal sinuses]].  The surface of the bone is ridged and porous and is covered with papillated [[Skin - Anatomy & Physiology#dermis|dermis]] that is continuous with the periosteum and [[Skin - Anatomy & Physiology#epidermis|epidermis]] which keratinises and forms the protective covering of the horn.  The substance of the horn is similar to that of the [[Hoof - Anatomy & Physiology|hoof]] and is a mixture of tubules and intertubular horn.  The new horn produced at the base is soft and often transparent and resembles the [[Hoof - Anatomy & Physiology|periople]] of the hoof, giving the horn a glossy appearance.

[[image: Horns.jpg|thumb|200px|right|Horns are commonly observed in Highland cattle, as pictured here]]

[[image: Horns.jpg|thumb|200px|right|Horns are commonly observed in Highland cattle, as pictured here]]

If the skin covering the horn bud is not removed, the horn will continue to grow throughout the animal's life from the base, apically.  Growth zones are visible with differing thickness of the keratin layer, relating to the nutritional status of the animal at that time.

If the skin covering the horn bud is not removed, the horn will continue to grow throughout the animal's life from the base, apically.  Growth zones are visible with differing thickness of the keratin layer, relating to the nutritional status of the animal at that time.

The dermis of the horn is supplied by the '''corunal nerve''', which is a branch of the [[Cranial Nerves - Anatomy & Physiology|maxillary nerve]] ('''CN V''').  This nerve is often blocked to provide local anaesthesia in the disbudding or de-horning process.

The dermis of the horn is supplied by the '''cornual nerve''', which is a branch of the [[Cranial Nerves - Anatomy & Physiology|maxillary nerve]] ('''CN V''').  This nerve is often blocked to provide local anaesthesia in the disbudding or de-horning process.

The primary function of horns is to convey social hierarchy.  The larger the horns, the higher up the social group the animal is.  They also have a thermoregulatory roll in cattle and goats.  When the ambient temperature increases, the blood flow through the dermis of the horn also increases, thus facilitating heat loss through radiation from the horn surface.

The primary function of horns is to convey social hierarchy.  The larger the horns, the higher up the social group the animal is.  They also have a thermoregulatory roll in cattle and goats.  When the ambient temperature increases, the blood flow through the dermis of the horn also increases, thus facilitating heat loss through radiation from the horn surface.