Veterinary Services Animal Health - Book 1 Notes

Animal Health Basic and Applied Anatomy and Physiology

This document contains notes on animal anatomy and physiology, compiled by Drs. Johan van Rooyen, Annelie Cloete, and Aileen Pypers, and reviewed on 01/02/2018. It covers various systems and structures of farm animals.

Introduction to Anatomy and Physiology

• Biology: Study of normal plant and animal life.

• Anatomy: Study of the composition and structure of the body and its tissues.

• Physiology: Study of the functions of organs and tissues.

• Embryology: Study of the development of a fertilized egg cell to an adult.

• Energy Acquisition: Animals require energy for growth, obtained from food.

  • Locomotory system: Enables movement to acquire food.

  • Senses: Used for smelling, seeing, and hearing to find food.

• Digestion:

  • The digestive system breaks down food into elementary substances (proteins to amino acids, carbohydrates to glucose, fats to fatty acids).

  • It includes structures and organs from the mouth to the anus.

  • It removes useful parts from food and discards the rest.

• Metabolism: Absorbed nutrients (amino acids, glucose, fatty acids) are changed into energy. The liver plays a significant role in this process.

• Respiration: Oxygen is required to "burn" nutrients for energy. The respiratory system supplies oxygen to the body.

• Circulation: The circulatory system transports oxygen from the lungs to the body and distributes nutrients. It also transports waste products of metabolism to excretory organs like the kidneys.

• Reproduction: The reproductive system is essential for reproduction.

• Endocrine System: This system consists of ductless glands that secrete hormones into the bloodstream. Hormones affect target organs, controlling involuntary processes like metabolism, growth, and digestion. The study of hormones is called endocrinology.

• Nervous System: Synchronizes and controls all systems.

  • Voluntary processes: Walking, vision, hearing, smell, etc.

  • Involuntary processes: Heart-rate, movement of the intestines, etc.

• Course Overview: A preview of different body systems to understand the normal healthy animal before discussing veterinary problems and diseases affecting farm animals.

Gross Anatomy: Terminology for Direction

The following terminology is used to describe direction on body parts:

• Dorsal: Towards the back or top line of a standing animal.

• Ventral: Towards the belly or lower part of the neck, chest, abdomen, pelvis, and tail.

• Cranial: Towards the head or cranium; to the front of an animal.

• Caudal: Towards the tail; towards the back of an animal.

• Median plane: Longitudinal, vertical mid-plane of the body.

• Dorsal plane: Horizontal plane running parallel to the dorsum and at right angles to the median and transverse plane.

• Transverse plane: Plane at right angles to the long axis of the body or body part.

• Palmar: Pertains to the palm of the hand; the surface of the front leg opposite the dorsal surface.

• Plantar: Pertains to the sole of the foot; the surface of the hind leg opposite the dorsal surface.

• Proximal: Of an appendage, nearer to the body.

• Distal: Of an appendage, further away from the body.

Histology

The basic building blocks of the body are cells. The study of cells is called histology.

• Animal cells are surrounded by a cell membrane.

• Each cell has a nucleus containing chromosomes.

• Chromosomes are strands of DNA carrying the genetic code.

• The cytoplasm is the collection of structures and chemicals surrounding the nucleus.

Physiology

Physiology is the study of the functions of the animal’s body.

• Almost all body functions can be explained by chemical reactions in cells.

• The study of these chemical reactions is called biochemistry.

• Ask "how does it work?" when observing animal body structures.

Pathology

When the normal functions of the animal body become abnormal, it is described as pathological.

• Pathology: The study of changes that occur in the body.

• Macroscopic changes (macropathology): Changes visible with the naked eye.

• Microscopic changes (histopathology): Changes visible through a microscope.

• Chemical pathology: Changes that are only chemical.

Clinical Procedures

Clinical procedures that can be performed on certain organs should be practiced.

Species and Breeds

This course examines the anatomy and physiology of ruminants, pigs, and horses. Differences in anatomy and physiology of dogs and birds will be mentioned when applicable.

Human Aspects

Anatomy, physiology, and health-related issues relevant to humans are also discussed.

Terminology

A list of Afrikaans, English, Xhosa, and Sotho terms is provided to improve communication among students from different language groups.

Self-Evaluation

Short tests should be completed without referring to notes. Review notes for any questions missed.

Task

1. Identify all anatomical structures observable on the outside of the animal.

2. Learn and use the terminology describing body regions.

3. Learn and apply terminology for describing direction on body parts.

4. Understand the function of selected structures on the surface view.

5. Describe selected clinical procedures.

Instruction

Identify the following structures and describe their function:

Identify the following regions of the body:

• Hindquarter

• Front quarter

• Neck

• Head

• Thorax

• Abdomen

• Flank

• Perineum

• Rump

• Triceps

Chapter 1: Section A - The Skin

• Objectives: Understand the anatomy and functions of the skin and associated structures.

• Introduction: The skin is the largest organ in the body by weight. If diseased, it can seriously affect the rest of the body.

Gross Anatomy

• The skin is continuous with the mucous membranes of the digestive, respiratory, and uro-genital tracts at natural openings.

• Consists of two layers: dermis and epidermis.

  • Epidermis: The outer layer, consisting of living cells covered by a layer of dead cells (keratin), which protects the softer layers below.

  • Dermis: The lower layer, containing hair follicles, sebaceous glands (which secrete oil to prevent drying), and wool fat (in sheep).

  • Hypodermis: Layer below the dermis where fat is deposited.

• The skin has many nerve endings for sensing the environment.

• Pigment: Gives color to the skin. Melanocytes contain melanin, which absorbs UV light and protects deeper structures.

  • Many melanin cells in the top layer result in black skin.

  • Many melanin cells in the deepest layer result in blue skin.

  • Diluted melanin or fewer melanin cells result in different shades of brown.

Physiology

Functions of the skin:

1. Protection:

   • Protects from fluid loss and injury from the environment.

   • The most important organ protecting against infectious diseases.

   • Adapts to environmental threats. For example, the skin on human feet thickens when going barefoot.

   • Hair and wool also form a barrier to damage from the environment.

   • Cavities in hair and wool fibers provide insulation.

   • Marine mammals have massive amounts of fat in the hypodermis for insulation.

   • Pigs use fat for thermal insulation in the absence of hair covering.

2. Sensation: Nerve ends feel fine touch, pressure, pain, heat, and cold.

3. Regulation of body temperature:

   • Absorbs heat from the sun and transfers it via the blood.

   • Loses heat when blood supply to the skin increases and the environment is colder.

   • Evaporation of sweat cools down horses and humans.

   • Dogs pant to cool down, lacking sweat glands in the skin.

Pathology

• The most common problem in the skin is cancers, apart from parasites and microbial infections.

• Squamous cell carcinomas (skin cancer): Often develop on unpigmented skin (white areas of cattle and sheep) due to radiation from the sun.

• Melanoma: A dark black color that occurs commonly in grey horses. It appears as a nodule and can spread rapidly. Also a serious cancer in humans with low levels of skin pigment.

• Rectal, vaginal, and uterine prolapse:

  • Can occur in all farm mammals.

  • The rectum moves through the anus, swelling up due to restricted blood drainage.

  • Often requires amputation or euthanasia.

  • Short tail docking is a major contributing factor.

  • Keep prolapses moist and clean. Icing sugar can help reduce swelling. Sutures can be placed to prevent recurrence.

• Mites: Burrow into the skin, causing severe irritation and fluid loss (e.g., sheep scab).

• Lice and ticks:

  • Lice either eat the outer layer of the epidermis or suck blood (blue louse).

  • Ticks penetrate the skin and drink lymph (immature ticks) or blood (mature ticks).

  • Ticks with long mouthparts can cause severe damage.

• Eczema: Irritated and damaged skin leads to fluid escape. In sheep, fluid dries out and forms wool clusters (lumpy wool disease).

• Photosensitivity: Irritating substances are created when plants are exposed to sunlight, causing inflammation and swelling (dikkop - swollen head).

  • If the plant contains poisons that damage the liver, it can lead to icterus or jaundice (geeldikkop - yellow swollen head).

• Keratosis: The keratin layer thickens and detaches due to irritation over a long time, or insufficient zinc or vitamin A (e.g., dandruff in Angora goats).

• Pigmentation: Protects against sunburn. Eyelids should be well pigmented to prevent swelling, irritation, and cancer.

Clinical procedures

• Teeth of farm animals: Determining the approximate age of animals

• When animals eat soft food, the teeth do not wear down, making it difficult to determine their age after 4 years (48 months). Hard and abrasive grazing can cause the teeth to wear down quickly, making animals appear older than they are at 4 years old. However, closely spaced teeth are an indicator of younger age, whereas older animals have teeth that start separating.

• Sheath and scrotum: The urethra opens externally in the head of the penis in males. The shaft of the penis, head, and processus urethralis are situated inside the sheath, ventral to the abdomen. The scrotum is situated caudoventrally under the abdomen, between the hind legs, and contains the testes.

• Vulva and vagina: The urethra opens in the floor of the vagina in female animals. The vulva is the external slit-like opening of the vagina situated ventrally to the anal opening underneath the tail. Mucous membrane color in female farm animals can be evaluated through the vaginal mucous membrane.

Species and breeds

• Generally, males have thicker skins than females; older animals have thicker skin than young animals. In very old animals (and humans), the skin becomes thinner due to atrophy.

• Average thickness of the skin of farm animals:

  • Sheep: $2.7mm$

  • Goats: $2.9mm$

  • Pigs: $2.2mm$ (The fat layer under the skin makes it appear very thick.)

  • Cattle: $6mm$

  • Horse: $1mm$ but up to $5 mm$ on the tail and mane.

  • Dog: $1mm$ or more. It is thicker over the head and neck.

• Cattle breeds from tropical areas have thicker skins than cattle breeds from temperate areas.

Self-evaluation

Ageing animals: Complete the following table:

Functions of skin: List the functions of the skin.

Terms and definitions: Complete the following list:

Chapter 1 Section B Associated Structures: Hair, horns and hooves

Objectives

1. Know the various types of hair of domesticated animals

2. Know the basic structure of the hoof, the horn and the claw.

3. Know the function and physiology of these structures

4. Know the Pathology of these structures and the impact on the farming system

Hair

Gross Anatomy

• Types of fibres

  • Two types of hair follicles are found on animals. Primary hair follicles and secondary hair follicles.

  • In dogs, cattle, horses, Cashmere goats and Boer goats the primary hair follicles are found throughout the year. The finer secondary hair follicles grow a softer and more protective coat in the winter months.

  • The secondary hair follicles are shed in the summer. This is called moulting. In Cashmere goats the secondary hair is combed out and used to produce a very soft and fine product.

  • In Merino sheep and Angora goats the primary and secondary hairs look the same and are present at all times. If the primary hair is thicker and without crimp it is referred to as kemp.

  • If a merino lamb does not receive sufficient nutrition in the uterus it forms less secondary hair and the wool cover may be less dense. Lambs that are born one of a twin or triplet also have a poorer development of wool on the belly and may appear to suffer from a “creeping belly” when the short wool reaches up onto the side of the body.

• Colours and markings of horses. Know at least the basic colours of horses: Black, Dark Bay, Bay, Chestnut, Liver Chestnut, Grey, Palomino and Albino

Histology

• Hair is made of keratin and develops in the epidermis. The colour in hair is formed from the same pigment, melanin that colours the skin.

Physiology

• Anaerobic nutrition of hair follicles.

  • In severely cold conditions the blood supply to the skin is restricted so that the animal does not lose too much heat. When this happens very little oxygen gets to the hair follicle and anaerobic breakdown of glucose provides the energy for the hair to keep on growing. If the animal does not get enough starches from the grazing the hair stops growing. Roughage provides energy in the form of acetic acid in the bloodstream but this cannot feed the hair follicle when it is very cold.

Pathology

• Mange or sheep scab – Mites can burrow into the skin and cause damage to the root of the hair. This will result in hair or wool loss.

• Ringworm – is not caused by a worm but by a fungus. Fungi can grow on the skin. The fungus penetrates the hair and the hair follicle causing it to become damaged and bare patches will be seen.

The hoof

Gross Anatomy

• The hoof is the horny covering of the distal digit and protects the blood vessels, nerves and other sensitive tissues of the last digit. All these structures together form the claw.

Histology

• The hoof is formed by the epidermis and is a very strong and flexible structure consisting of keratin.

Physiology

• The foot pump

  • The sole of the hoof is dome shaped. When the animal puts it foot down the sole presses down and the wall of the hoof expands slightly. This action helps to pump blood through the foot. In Saddle horses, the very long hooves with very heavy inflexible shoes mean the hoof cannot act as a pump and too little oxygen gets to the foot. This can lead to damage to the bones, joints, soles and hooves.

Pathology

• Foot rot - Foot rot is caused by bacteria that can live in moist ground or dirty paddocks. These bacteria digest the hoof and create a passage along the white line. It can penetrate and damage the hoof right up to the coronary band. When pressure is applied to the hoof smelly grey pus will become visible at the point where the foot rot started, usually under a fold of hoof that has grown over the sole. Footrot can be controlled with an antibiotic injection and a foot bath of Zinc Sulphate.

• Foot abscess - Foot abscess is not the same as footrot. In some cases footrot can turn into an abscess. Foot abscesses can also be caused by tick bites or thorns. The abscess is very destructive and causes great damage to the joints and other structures inside the hoof. Treatment consists of cleaning out the abscess and spraying an antibiotic aerosol into the cavity. The foot eventually becomes malformed and the animal often remains lame.

• Growth rings - Lack of sufficient food or disease may cause growth rings to form on hooves. The hoof grows about 1 cm per month and it is therefore possible to look at the hoof of an animal and determine how long ago it had been sick. Cows with horns make clear rings on the horn every time she raises a calf. It is possible to determine how many calves a cow has had in her life.

Horns and hooves

• The hoof is the horny covering of the distal digit and protects the blood vessels, nerves and other sensitive tissues found here. All these structures together form the claw. The horn is a growth of bone, covered by skin with a very thick layer of keratin covering it.

Physiology

• Research the ways in which African antelope species use their horns to regulate their body temperature.

Pathology

• We will cover this in the farm procedures section when we discuss dehorning.

Clinical procedure

• Trimming sheep and goat claws - The side wall of the hoof often grows long and curls in under the sole. The hoof remains moist and footrot can occur. This fold should be cut away. In old sheep and goats the toe grows out very long and also may need to be trimmed. Care must be taken not to cut into the live part of the hoof. This will cause bleeding and lameness.

• Trimming cattle claws - Cattle claws rarely need trimming if cattle run on hard and rocky ground. In sandy areas and in animals that are kept in a stable or in a small pen the hoot may grow out long and even curl back. Trimming is then done with clippers or by sanding the hoof down with a small angle grinder with sandpaper. Your veterinarian my need to help you to give an anesthetic to big cows and bulls.

• Dehorning cattle and sheep - Dehorning of calves, kids and lambs should be done when the horns are still small. Burning with a gas burner destroys the growth ring of the horn and it should not grow out again. In adults dehorning is done with a cutting wire (Embryotomy wire) or a Keystone cutter. The wire method makes it possible to cut away the growth area so that the horn does not grow again. These methods should only be performed under the supervision of a veterinarian as they are painful and therefore require nerve blocks. In adult cattle and rams the horn may be hollow and after cutting the horn there may be a big hole in the skull allowing access of dirt and flies to the frontal sinus. The hole can be plugged with cotton wool and stockholm tar.

Study Aid

Identify the following structures on the X-ray.

• Pedal bone

• Coffin bone

• Wall of the hoof

• Sole of the hoof

• The heels

• Navicular bone

• Pastern

• Coronary band

Species and breeds

• Pigmented claws vs. unpigmented claws. White hoof is often softer than black hoof. Horses and cattle with black hooves have less wear on their hooves and get injured less than those with white hooves.

• Desert animals tend to be more prone to footrot than breeds that originated in areas with high rainfall. Over many years animals that develop footrot in high rainfall areas have been culled naturally. When a breed that originated in desert areas, for example the Blackheaded Persian sheep, is kept on irrigated pastures, many develop footrot. After time the flock becomes more resistant because the susceptible individuals are culled and their contribution to the gene pool becomes smaller.

• Polled vs. horned. Some species may lack horns and only breed offspring without horns. These are the polled breeds for example: Polled Dorset, Red Poll, Tuli, some Herefords etc.

• The horned breeds breed offspring with horns for example Shorthorns, Nguni, Drakensberger, and Merino. Horns grow bigger in male animals than in females and in some breeds the female may lack horns or have very small horns only.

Human aspects

• A zoonosis is a disease that can spread from animals to humans. Ringworm in animals can spread to humans. Children and woman seem to be more susceptible.

Self-evaluation

Give a short description of each of the following:

1 Horn
2 Hoof
3 Footrot
4 Foot abscess
5 Kemp
6 Cashmere
7 Creeping belly
8 Pedal bone
9 Ringworm
10 Foot pump

Want to know more?

• Synthetic fibers are becoming a serious threat to the future of wool and mohair. It is now possible for factories to create artificial fibers that are hollow and have the same ability to keep humans warm.

• Wool processing needs a lot of water for the washing of the wool and foreign seeds can end up in the countries that buy our wool. Poisonous residues such as insecticides and arsenic can also become a problem for factories.

• The factories that manufacture artificial fibers use coal or crude oil as the source of the chemicals from which they create the artificial fibers. They also face problems in the future as oil and coal becomes scarce.

• Wool and mohair farmers should take care that their products are not contaminated with chemicals and other foreign material that can cause problems for the factories that process our wool.

• Rhino horns are not the same as those of cattle. In the rhino the horn is formed by thousands of hair that grow attached to each other. Rhino horn is very popular in the eastern countries and many rhino are killed only to get hold of the horn which sells for thousands of dollars per kg.

What to expect from here:

• We are now going to study the structures and systems which are found underneath the skin and are therefore not necessarily visible from the outside. Under the skin of the animal one finds the hypodermis with fat tissue in which superficial lymphnodes are embedded, such as the pre-scapular, prefemoral and popliteal lymphnodes. These form part of the lymphatic system of the body. Muscles, which form part of the locomotory systems of the body are found underneath the hypodermis.

Chapter 2: The Skeletal System

• Objectives: Know the large bones of the skeletal system.

• Introduction: The locomotory system includes the skeleton with its joints, which give support to the different bones as well as the muscles. Muscles contract and relax under the control of the nervous system, resulting in movement. Ligaments and tendons support and protect the muscles by preventing overstretching.

Gross anatomy

• Bones of the body are divided into four categories:

  • Long bones (e.g., humerus, femur).

  • Flat bones (e.g., cranial bones, ribs, scapula).

  • Short bones (e.g., carpus, tarsus).

  • Irregular bones (e.g., vertebrae).

• Long bones: Elongated and cylindrical structures with large extremities covered with articular cartilage. Covered by a strong membrane called the periosteum, which is responsible for increasing bone diameter during growth.

• The skeleton is a framework of hard structures or bones that support and protect soft tissues. It consists of bones, cartilage, and ligaments.

The skeleton is divided into two parts:

Axial skeleton

• Includes the cranium, vertebral column, ribs, and sternum.

Appendicular skeleton

• Comprises the pelvic girdle, hind limbs, and front limbs.

1 The Skull

The skull is divided into:

• Cranium: Bones fused together to enclose and protect the brain and inner ear. Consists of flat and irregular bones.

• Facial bones: Fuse with cranial bones to form oral and nasal cavities and the upper jaw.

• Mandible or lower jaw: In horses, consists of two halves fused together, while in ruminants, the two halves do not fuse completely. Teeth are situated in sockets in the upper and lower jaws.

• Four types of teeth: incisors, canines, premolars, and molars. Age of an animal can be determined by examining the teeth

2 The vertebral column

The vertebral column consists of:

a) Cervical vertebrae (7)
b) Thoracic vertebrae (13) (18 in the horse)
c) Lumbar vertebrae (6)
d) The pelvic girdle is formed by the sacrum, and the pelvis which consists of 3 fused bones - the ilium, pubis and ischium.
e) Coccygeal vertebrae.
f) The ribs. The upper extremities of the ribs articulate with the bodies of two adjacent thoracic vertebrae. Most of the ribs are attached to the sternum (breast bone) at their lower ends. In this way a cage is formed for the protection of the heart and lungs. Although the liver is not situated in the thoracic cavity it is also to a large extent protected by ribs. Ribs are flat bones.
g) The sternum or breastbone. The ventral extremities of the ribs are attached to the sternum.

3 The front leg

a) Shoulder-blade (scapula) which is attached to the body by muscles only. This is why the scapula has a flat, fan-like structure. The dorsal part of the scapula has cartilage attached to it.
b) Upper arm bone (humerus)
c) Fore arm bones – consists of two bones i.e. the radius and ulna.
d) Carpal bones – this is equivalent to the wrist.
e) Metacarpal bones (cannon bone) – this is equivalent to the hand bones.
f) Phalanges or finger bones. In the horse only the middle finger remains. In cattle, sheep and goats only the middle and fourth fingers are left. The hoof is homologous to the fingernail of humans. The function of the front legs is mainly that of a carry and catch lever mechanism. They carry about 60 per cent of the body mass. The bones are pillar-like and placed in a fairly straight line so as to support the