Vet Form and Function Notes PDF

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Summary

Core modules for 2nd-year bioveterinary students...

Description

Introduction to veterinary anatomy Anatomical planes Sagittal Plane - Runs the length of the body - Divides into left and right portions which are not necessarily of equal size Median Plane - Runs the length of the body as a mid-sagittal plane - Dividing body into equal halves Transverse Plane - Divides the body into - Cranial (head end) - Caudal (tail end) - Parts not necessarily equal size Dorsal Plane - Divides the body into - Dorsal (towards back) - Ventral (towards belly) - Parts not necessarily equal size Anatomical directions - The following terms can be used to describe a fixed point, and retain relevance regardless of the animal’s posture • Arranged in opposing ‘pairs’ • Describe relative (not absolute) positions Cranial - Towards the head Caudal - Towards the tail For the head Rostral - Towards the nose Caudal - Towards the back of the skull Dorsal - Towards the spine, and corresponding surfaces of the head and tail Ventral - Towards the sternum, and corresponding surfaces of the head and tail Medial - Towards central, median line

Lateral - Away from central, median line The median plane divides animals down the middle into a left and right half Proximal - Close to the trunk - Towards the top of the limb Distal - Away from the trunk - Towards the bottom of the limb Limb specific terms On the forelimb Below the carpus - Caudal becomes palmar - Cranial becomes dorsal On the hindlimb Below the tarsus - Caudal becomes plantar - Cranial becomes dorsal Axial - Close to axis of central digit, or between the central two digits. Abaxial - Away from this axis

Anatomical actions Movement occurs at joints Flexion - Reduces the angle between two parts Extension - Increase the angle between two parts Spine – also ‘jointed’

Abduction - Movement away from the median plane - Often combine with a little bit of rotation - Cranial edge moves laterally Adduction - Movement towards the median plane Pronation - Turning the foot so that the palm/sole faces downwards Supination - Turning the foot so that the palm/sole faces upwards Skeleton Axial skeleton - Components lie on the midline - Consist of - Skull - Vertebral column - Ribs - Sternum Appendicular skeleton - Consist of - Forelimb - Hindlimb - Respective ‘Girdles’ Vertebral Column Regions Cervical - Dog - 7 Thoracic Vertebrae - Dog- 13 - Articulate with the ribs Lumbar vertebrae - Dog - 7 Sacral vertebrae - Dog – 3 - Fused to form single structure overlying the pelvic cavity

AXIAL APPENDICULA R

Caudal/Coccygeal vertebrae - Dog – variable 20-30 Body cavities Two main cavities

DORSAL BODY CAVITY

Dorsal Body Cavity - Containing brain and CNS - Cranial activity – housing the brain - Spinal activity -Housing the spinal cord

VENTRAL BODY CAVITY

Ventral Body Cavity - Much larger and contains visceral organs - Thoracic cavity - Abdominal cavity/Pelvic cavity Thoracic cavity - Contains the lungs, heart, great vessels, nerves and the thoracic portion of the oesophagus and trachea - Divided into two halves - Lined with pleura (each of a pair of serous membranes lining the thorax and enveloping the lungs in humans and other mammals. - Bordered by - Ribs dorsally and laterally - Sternum ventrally - Diaphragm caudally - Thoracic inlet cranially Abdominal/Pelvic cavity - Contains the visceral organs of - Digestive system - Urinary system - Reproductive system Lined with peritoneum - Bordered by - Diaphragm cranially

Abdominopelvic cavity Pelvic cavity

Abdominal cavity

Body cavities - The pleura and the peritoneum (and pericardium) are thin sheets of serous membrane which line the body cavity and cover the organs - Visceral is the name given to the layer covering organs (i.e. the inner layer) - Parietal is the name given to the layer further away from the organ (i.e. the outer layer) - There is a very small amount of fluid between these two layers - Reduces friction and allows movement

Structure and function of the musculoskeletal system Locomotor system - Gives form, support, stability and movement to the body Components - What provides the following? Rigid stability and support - Bones (osteology) Movement - Joints (Arthrology) Form, Stability and movement - Muscles (Myology) • -

Bones Give support to an animals form, and provide attachment points for muscle

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Joints Area of movement. Different types have different functions

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Ligaments Attach bone to bone

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Tendons Attach muscle to bone

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Muscle Provide the power for movement. Contraction or relaxation of the muscle has an affect on the angle of the corresponding joint

4 mains ‘types’ of bone • Flat bone • Long bone • Short bone • Sesamoid bone Flat bone - Scapula - Pelvis •

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Features Large surface area for muscle attachment Gives protection to underlying structures

Long bone - Humerus - Femur

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Features Support for limb musculature Leverage of limbs

Short bone - Carpal bones - Tarsal bones • -

Features Allow wide range of movement Anti-concussive

Sesamoid bones • Examples - Patella • -

Function Located along course of a tendon Redirect forces and reduce friction at points where there is a change in angle of the bony surface

Bone anatomy • Bones have • Rough surface areas • For general muscle attachment • Specific bony contours • Processes, tuberosities, tubers, tubercules • Provide specific attachment sites for important structures

Gross anatomy of a long bone - Epiphysis/epiphyseal region - Metaphysis - Diaphysis/diaphyseal region - Cortex • compact bone - Medullary cavity • contains bone marrow - Periosteum • Thin but tough layer on outer surface • Contains osteogenic cells - Endosteum • Covers the inside of bones • Surrounds medullary cavity - Articular surfaces Bone growth • 2 methods of bone formation - Intramembranous - Endochondral

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Limb bones form from centres of ossification Endochondral ossification (c.f intramembranous)

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In young growing animals, Cartilage between the centres appears black on radiographs – don’t mistake for fractures! Epiphyseal growth plates

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Young animal has open physes, with epiphyseal growth plates Produce increase in bone length

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Mature animals have closed growth plates – physeal scars Time of closure depends on contribution of growth plate to limb length/bone size Can estimate age from growth plate closure times

Growing animals - Epiphyseal plates responsible for the increase in bone length Cells of bone and articular surfaces Bone cells

Bone Osteogenic cells - involved in active bone formation, stimulation results in production of osteoblasts Osteoblasts - Active cell which produces bone matrix and helps to calcify it Osteocytes - mature bone cells Osteoclasts - bone reabsorbing cells Consists of varying numbers of these cell types surrounded by bone matrix Bone matrix is much more solid than other intracellular matrix types due to its high content of mineralised substances - Calcium phosphate - Calcium carbonate - Hydroxyapetite Collagen and elastin fibres give some flexibility and strength – prevent bones being shattered Cartilage -

Strong, dense but flexible tissue

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Found in many areas • Nose, ear, intervertebral discs, rib cage etc.

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Consists of cells called CHONDROBLASTS

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Which are enclosed within an extracellular matrix rich in: • Collagen • Elastin • Proteoglycans

Different types depending on amounts of three main components • Elastic cartilage • Principle component: Elastin • Makes up part of larynx and ear flap • Hyaline Cartilage • Principle component: Collagen • Found on articular surface of bones • in the respiratory tract and on ends of ribs • Fibrocartilage • Principle component: contains type I and type II collagen • Found in intervertebral discs, pubic symphysis and TMJ Joints -

Flexion Extension

Joints can be grouped by either - Function - Structure

Fibrous joints - Usually no or very little movement occurs • Synarthroses/amphiarthroses -

Thick connective tissue at articulations

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Examples • Bones of the skull

Cartilaginous joints

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Usually little or no movement • Cartilage at articulations

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Examples • Pubic symphysis • Vertebrae

Synovial joints - Generally, allow for a wider range of movement - Characterised by • the presence of articular cartilage on the bone ends. • Which type?? • The presence of an articular capsule filled with synovial fluid Hyaline cartilage

Types of synovial joint - Six types of synovial joint • Pivot - Provides ROTATION • Rounded end of one bone fits into a ring formed by another bone • Example: joint between 1st and 2nd neck vertebrae • Gliding • Where joint articulation is flat or nearly flat • Example: wrist bones • Ball and socket – provide rotation • Where round end of one bone fits into a socket formed by the other • Example: hip joint, shoulder joint • Hinge - Provides flexion/extension • One bone moves while the other stays stationary • Example: elbow joints • Condyloid – provides circular motion, flexion and extension • Example: between radius and carpal bones • Saddle – provides flexion and extension • Example: thumb – allows us to have opposable thumbs

Support for joints

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Provided by ligaments • Dense fibrous connective tissue • Join bone to bone Collateral ligaments support the joint • Usually medial and lateral

Muscle Tissue -

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Major component of the locomotory system • Also has other (very important!) functions • Function is to shorten or contract • Produces movement 3 Main types • Skeletal (striated) muscle • Smooth muscle • Cardiac muscle

Skeletal/striated muscle -

Involved in locomotion Attached to rigid structures – usually bone! Contains long muscle cells that run the entire length of a muscle fibre Multinucleated cells Made up of repeated units called SARCOMERES • These contain actin (thin) and myosin (thick) filaments • This gives the muscle its ‘striated’ appearance

Attachment of muscle

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4 main methods • Via tendons – limb muscles • Condensation of deep fascia into cords. • Allows small area for attachment - Useful across joints, less bulky • Directly to bone • Usually to flat bones with rough surface area, or with bony tuber • Via aponeurosis • Condensation of deep fascia into sheets • Long attachment point • Usually where muscles have limited access to bone • Via fascia • Least common means – found in cervicothoracolumbar fascia • Connective tissue as an extension of the deep fascia

Via tendons

Directly to bone

Digestion and excretion

Via aponeuroses

Ingestion - Taking in substances into digestive tract (food, water) Digestion - Break down of large molecules to small water-soluble molecules to be absorb across the gut wall into the bloodstream Absorption - Absorption of end products of digestion across the microvilli of intestine Egestion - Getting rid of indigestible waste product Excretion - Metabolic waste Physiology • Excretion • broadly similar between species • Digestion • very different across the different species Anatomy overview Excretory organs? • Kidneys • Cortex • MEdulla • (Skin) • (lungs) Digestive organs • Mouth • Oesophagus • Stomach • Small intestine • Large intestine • Accessory organs • Liver (excretory?) • Pancreas

Physiology overview

Excretion involves • Renal blood flow • Glomerular function • Tubular function Digestion • Motility • Digestion (chemical breakdown) • Absorption • Metabolism Extracellular water INTERSTITIAL 25% of total body water (65% of extracellular fluid volume)

Overview of excretion Distribution of fluid within the body • Extracellular • Blood • Interstitial fluid • Intracellular For normal function, volume and composition of extracellular fluid must be maintained within narrow physiological limits

Extracellular water PLASMA WATER 8% of total body water (25% of extracellular fluid volume)

Intracellular water 67% of total body water

Total body water 60% TBW

Which organ is largely responsible for maintaining this balance? • Kidneys They do this by • Stabilising osmolarity and volume of extracellular fluid • Regulating concentration of extracellular ions • Removing metabolic waste products and foreign substances • Maintaining acid base balance Gross anatomy of the kidney

Renal capsule • Smooth transparent membrane closely attached to the surface of the kidney Renal cortex

• Outer ‘layer’ of the kidney – contains functional kidney tissue Renal medulla • Inner ‘layer’ of the kidney – contains tubular tissue Renal pelvis • Expanded area of ureter

Functional anatomy of the kidney Basic functional unit of the kidney = nephron • This consists of • Capillary network – the glomerulus • A tubular system • The glomerulus • is located in the renal cortex • The tubular system • extends into the renal medulla Physiology of excretion The kidneys achieve their function via • Filtration • Bulk flow • Indiscriminate • Reabsorption • Selective reabsorption of valuable substances • Secretion • Further secretion of substances above and beyond those which have been filtered

Urine • The end product of excretion = urine • Transferred from kidneys to bladder • Via ureters • Bladder • Temporary storage organ until urine is voided (not all species!)

Digestion The process by which food is broken down into small enough molecules to be absorbed by the body This breakdown can be achieved • Mechanically • Chemically Mechanical breakdown • Prehension - The action of grasping or seizing • Mastication - Chewing • Motility Chemical breakdown • Secretion • Digestion Absorption (metabolism) Egestion (defaecation) Overview of digestion Mechanical breakdown, secretion, motility, digestion, absorption, egestion For each of these think about which occur at each point in the digestive system…. • Teeth • Salivary glands • Stomach • Liver/gall bladder/pancreas • Small intestine • Large intestine Digestive physiology – head Prehension

• Movement of food into the oral cavity Mechanical breakdown • Mastication reduces size of food particles • Dentition differs between species depending on their diet Salivation • Mucus to lubricate food • Saliva contains amylase in some species to begin the digestion of carbohydrate Saliva Various salivary glands • Parotid = serous • Mandibular, sublingual, buccal = mixed mucous and serous • Zygomatic = mucous carnivores only! Simple stomached animals • Mainly mucous to aid passage of food • pH neutral to allow action of amylase Complex stomached animals (ruminants) • Mainly serous to provide optimum conditions for fermentation • Ph alkaline to buffer forestomach for fermentation • Copious secretions Salivary composition • Dependent on diet and which glands are stimulated • Mucin (+ water = mucous) • Amylase (omnivores/horses/ruminants) • Bicarbonate (neutralisation/buffering) • Phosphate (ruminants) • Lysozyme/antibodies (reduce infection risks) • Protein binding tannins (leaf and bud eaters) • Urea (ruminants) Salivary secretion Non ruminants • 1◦ secretion Isotonic with blood • At low flow rates • Becomes hypotonic • At high flow rates • Remains isotonic Ruminants • Secretion always isotonic • At low flow rates • PO4 dominates • At high flow rates • HCO3 dominates Regulation of salivary secretion

Entirely under neural control (cf other digestive juices) Sympathetic supply – fight or flight! • REDUCTION in flow of saliva Parasympathetic supply – rest and digest! • Increase in the flow of saliva Basal salivary secretion for oral hygiene 2 reflex pathways • Congenital (innate) • Conditioned (learned) Digestive physiology – abdomen Motility • Segmental contractions • breakdown and mix • Peristaltic contractions • move food in a general aboral direction, at a rate which allows sufficient time for digestion/absorption • Anti-peristaltic contractions • Move food in an oral direction • Some species – slows food to allow sufficient digestion/absorption • Ruminants – to allow rumination, chewing the cud! • Protective – vomiting! • Mass movement • Extended peristaltic contractions used to empty sections of GI tract Chemical breakdown Secretion of digestive juices • Where do these come from?? Composition • Ions and ph appropriate for action of digestive enzymes • pH in stomach = 2 for protein digestion • Enzymes in SI want ph 6-7 • Mucus to lubricate food and protect mucosa • Enzymes for chemical breakdown of food Digestive juices extensively reabsorbed Digestion (chemical breakdown of food) Enzymes • Carbohydrates – amylase, disaccharidases • Saliva, pancreas, intestinal mucosal surface • Protein – pepsin, trypsin, peptidases • Glands of stomach, pancreas, intestinal mucosal surface • Fat – lipase, phospholipase

• Pancreas, intestinal mucosal surface Secretions break down large food components (e.G. starch to disaccharides) Digestion of smaller food components occurs at mucosal surface to facilitate absorption (e.g. disaccharides to monosaccharides) Absorption Is selective • Most nutrients require specific transporter proteins Active transport of nutrients • Directly: by primary active transport • Indirectly: by secondary active transport Passive transport of nutrients • Facilitative via transporter protein • Diffusion down a concentration gradient Egestion Passage of undigested food from the body

Physiology of the GI tract Intestinal motility – types Peristaltic - Moving food away from mouth to anus Segmental Anti-peristaltic - Move backwards in digestive tract (vomit) Mass movement - Emptying the entire section in GI tract Peristaltic Longitudinal Muscle Circular Muscle

Segmental

Motility in dog stomach Simple stomach Spontaneous peristaltic like waves • Mix food with digestive juices • Move food through stomach and towards small intestine Motility in Small and large intestine (of the dog) Segmental contractions occur in small and large intestine • Acts to churn and mix ingesta • Can help to slow passage of chyme through GI tract Motility in bovine stomach Complex stomach – four chambers • Rumen, Reticulum, Omasum, abomasum Primary contractions • Mixing of food - rumenoreticular • Main type of contraction Secondary contractions • Eructation – movement of gas out of stomach • Occur after every few primary contractions Rumination contractions • Allow regurgitation of food for rechewing (rumination) • Reticular contraction which is separate from primary contractions

Motility in horse large intestine

Types of food All three provide energy, and all three are broken down into their basic units by digestion in the small intestine Carbohydrate Fat Protein Carbohydrates Consist of • Carbon • Oxygen • hydrogen Classified as • Monosaccharides • Disaccharides

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Polysaccharides

Monosaccharides – most simple • Made up of only one five or six carbon unit Disaccharides • Made up of two molecules of monosaccharide Polysaccharides – most complex • Contain multiple numbers of simple sugars (monosaccharides) • Hydrolysable eg starch • Non-hydrolysable eg cellulose Monosaccharides

Disaccharides

Polysaccharides

Proteins Consist of • Carbon • Hydrogen • Oxygen • Nitrogen Classified as • Amino acids (monopeptides) • Dipeptides • Tripeptides • Poly/oligopeptides Monopeptides – most simple • Amino acids – single building blocks of protein These undergo dehydration synthesis (cou...