ANS 206 practical 1

Label 1-4

5 functions of the skeletal system

1. Support: the hard framework of the skeletal system helps to support and anchor the soft organs

2. Protection: the skeletal system surrounds the organs, for example the brain and spinal cord, and provides protection

3. Movement: muscles are able to attach to the skeletal system, this allows bones to be used as levers

4. Storage: minerals and lipids are stored within bone material

5. Blood cell formation: bone marrow is responsible for blood cell production

Compact Bone

hard layer that covers most bones and forms the shaft of long bones. Compact bone contains both bone cells and blood vessels.

Cancellous (or Spongy) bone

located at the ends of long bones and is composed of spicules arranged in a porous network. The small, open spaces are then filled with marrow.

Medullary Cavity

space that is found inside the cortex of a long bone. In a young animal the medullary cavity is filled with red marrow, this will eventually be replaced by fatty yellow marrow as the animal ages.

Bone types

long

Short

Flat

Irregular

Sesamoid

Long bone anatomy

1. Epiphysis: this refers to the ends of the long bone. Each long bone has a proximal epiphysis and a distal epiphysis.
   
   

   • Proximal epiphysis - end closest to the body

   • Distal epiphysis - end furthest away from the body

2. Diaphysis: the shaft of the long bone, found between the two epiphyses and surrounds the medullary cavity.

3. Articular Cartilage: thin layer of hyaline cartilage that covers the end of the bone that articulates, cushions and allows for smooth movement.

4. Epiphyseal Plate: layer of cartilage that allows for the growth of the bone, this is the only area where a bone can lengthen. Separates the diaphysis and epiphysis in an immature bone. 

Functions of long bones & examples

• act as levers

• aid in support, locomotion, and prehension

The best examples of long bones within the bones are the bones in the extremities such as the humerus, radius, and ulna in the forelimb and the femur, tibia, and fibula in the hindlimb.

Functions of short bones & examples

Short bones have a cube-like structure with no single marrow cavity. Instead, these bones are filled with spongy bone filled with marrow spaces.

• absorb concussion and shock

• In carpus & tarsus (found in complex joints where they can also provide a variety of movements)

Functions of flat bones & examples

There is an inner framework of spongy bone, called diploe, sandwiched between two plates of compact bone. These two plates are called the lamina externa and the lamina interna. 

• provide protection to vital organs such as the brain (skull), the heart and lungs (scapula and ribs).

• The scapula provides large areas for attachment of muscles.

Functions of irregular bones & examples

unpaired bones found on the median plane that have an odd shape

• provides protection, support, and muscular attachment. 

• Ex: vertebrae & pelvis.

Functions of sesamoid bones & examples

small, independent

Generally, sesamoid bones are found embedded in a tendon where they help to reduce friction, increase leverage, or change the direction of pull. 

Ex: patella (or kneecap) and the distal sesamoid bone.

Three small bones found within soft organs:

• Os penis - bone in the penis of dogs

• Os cordis - bone in the heart of cattle

• Os rostri - bone in the snout of pigs

Axial Skeletal System

• Skull

• Vertebral Column

• Sternum

• Ribs

These bones are important for protection, support, and carrying other body parts.

Appendicular skeletal System

• Thoracic limbs (forelimb)

• Pelvic limbs (hindlimb)

• Shoulder 

• Pelvis

The two skeletal systems articulate at one point, this is the…?

sacroiliac joint or SI. This is where the sacrum of the vertebral column articulates with the ilium.

Vertebrae labeling

Horse vertebral formula

C7 T18 L6 S5 CL15-20

Pig vertebral formula

C7 T14-15 L6-7 S4 CL20-23

Dog vertebral formula

C7 T13 L7 S3 CL20-23

Appendicular skeleton

• Shoulder - pectoral girdle (scapula)

• Forelimbs - humerus, radius, ulna, carpals, metacarpals, phalanges

• Pelvis - pelvic girdle (ilium, ischium, pubis)

• Hindlimbs - femur, tibia, fibula, tarsals, metatarsals, phalanges

Forelimb & label

The forelimb is made up of the:

1. Scapula, shoulder blade 

   • relatively flat, triangular bone

   • has a spine that extends to the dorsal border and divides the scapula unevenly into two portions 

   • the distal end of the spine forms the acromion process

   • it is attached to the body via muscle, ligaments, etc. we call this a synsarcosis - there is no true joint

2. Humerus

   • a long bone that has a shaft and two extremities

   • proximal end has a rounded head that articulates with the scapula to form the shoulder joint, or scapulohumeral joint

   • Humerus + scapula = shoulder joint

   • The distal end of the humerus forms the elbow joint with the proximal ends of the ulna and radius

3. Radius and Ulna (forearm)

   • Radius is larger, proximally it forms the elbow with the humerus and distally articulates with the carpus

   • Ulna forms the olecranon process (point of elbow); in horses the ulna and radius is fused; ox, sheep, goats, dogs, cats have a complete ulna

4. Carpus - often referred to as the knee, this region corresponds to your wrist. The carpus consists of two rows of small bones called carpal bones.

5. Metacarpus - immediately distal to the carpus, in the horse it is often referred to as the cannon bone. Two small splint bones are found next to the metacarpus, one on the medial side and one on the lateral side. Metacarpus + Proximal Phalanx = Metacarpophalangeal 

6. Digits - 

   • Made up of three phalanges: proximal phalanx, middle phalanx, distal phalanx. In horses, these three bones are often referred to as the long pastern, short pastern, and coffin bone. 

   • Proximal phalanx + middle phalanx = fetlock joint or proximal interphalangeal - two sesamoid bones are located here called the proximal sesamoid bones

   • Middle phalanx + coffin bone = pastern or distal interphalangeal

   • The distal sesamoid bone, or navicular bone, is located between the middle and distal phalanges

Pelvic girdle/Os Coxae & label

the fusion of 3 different bones:

1. Ilium - the largest and most dorsal portion

   • Tuber Sacrale - close to the sacroiliac joint, where the sacrum and ilium articulates

   • Tuber Coxae - point of hip, or hook bone in cattle

   • Wing - flat portion between the tuber coxae and tuber sacrale

   • Fracture of the tuber coxae in horses is called knock-down hip

2. Ischium - forms the caudal part of the floor of the pelvic cavity

   • Ischial tuber - pin bone in cattle

3. Pubis - smallest, forms the cranial part of the floor

Hindlimb & label

The bones of the hindlimb include:

• Femur - thigh bone

  • head articulates with the acetabulum of the Ox Coxae to form the hip joint

  • distally, the bone has two condyles that articulate with the patella and the tibia and fibula

• The tibia and fibula are fused in horses

  • the tibia is the larger bone

  • Femur + tibia + patella = stifle, corresponds to the knee joint in people

• Tarsus or hock joint

  • consists of multiple small bones called tarsal bones

  • The two largest bones of the hock are the talus and calcaneus, the calcaneus process makes up the point of hock

• The metatarsus (cannon) and digits are identical to the forelimb

Masseter muscle

involved in mastication, or chewing; broad muscle in the cheek of the horse

Trapezius (what does it act on & what are the two portions?)

Acts on the Shoulder Girdle

This muscle acts on the scapula

Trapezius - swings the scapula forward

• It has two portions: cervical and thoracic

List the extensors acting on the shoulder joint

Brachiocephalicus (head to arm) and the Supraspinatus

List the flexors acting on the shoulder joint

the Latissimus Dorsi and the Infraspinatus.

List the adductor and the abductor of the shoulder joint

adductor: Pectoralis

abductor: deltoideus

Triceps brachii

Muscle that extends elbow joint

Biceps brachii

Flexes elbow joint

Hamstrings (in relation to the hip joint)

extensors of the hip joint

Made up of 3 muscles!

• Bicep femoris, Semitendinosus, Semimembranosus

Quadriceps (in reference to the hip joint)

Flexors of the hip joint

Gluteal muscle

Abductor of the hip joint

Quadriceps (in relation to the stifle joint)

Extensors of the stifle joint

Hamstrings & gastrocnemius (in relation to the stifle joint)

Flexors of the stifle

Gastrocnemius (In relation to the hock joint)

Extensor of the hock

Latissimus dorsi

Strong flexor of the shoulder

Will advance the trunk if the limb is fixed

external abdominal oblique

the most superficial muscle

helps to flex the vertebral column, support the organs of digestion and reproduction

Role of diaphragm and intercostals

Involved in respiration

define extension, flexion, adduction, & abduction

• Extension: Straightening or increasing the angle

• Flexion: Bending or decreasing the angle

• Adduction: Moving towards the midline

• Abduction: Moving away from the midline

What is the endocrine system

made up of a group of ductless glands that secrete hormones

What is a hormone?

A hormone is a chemical substance that is produced by a ductless gland, this substance is then released into the blood stream and carried to other parts of the body where they will produce a specific regulatory effect.

three ways hormones are secreted

Endocrine route

Exocrine route

Paracrine route

Endocrine route

the hormone will be transported via the blood stream to the target organ

Exocrine route

the hormone is secreted into ducts then it travels to outside the body where it interacts with a target organ. For example, hormones will be secreted into the lumen of the digestive tract.

Paracrine route

the hormone will be secreted into the space between cells and the interstitial fluid will then carry it to the target organ; these hormones often effect neighboring cells

Chemical structures of hormones

Classic hormones can be grouped based on their chemical structure as either peptides (protein), amines (modifications of tyrosine), or steroids (cholesterol).

Where are peptide hormones and amines stored?

stored in secretory granules by endocrine cells

Can steroid hormones be stored?

NO, must be synthesized

Hormones NOT Secreted by Endocrine Glands

Gastric

Secretin

Erythropoietin

Gastric

released from the wall of the stomach; stimulates the release of gastric juices from gastric glands for digestion to being

Secretin

released from the wall of the small intestine; stimulates the secretion of intestinal/pancreatic juices to continue digestion in duodenum

Erythropoietin

released by the kidney; stimulates bone marrow

Target organ

Only certain populations of cells will respond to an individual hormone

target organ identifies the tissue whose cells will be affected by a given hormone.

Cells within target organs can recognize and respond to a given hormone because they contain specific receptors capable of binding with the hormone.

Hormone Receptor

A receptor for a specific hormone must be present for a cell to respond to the hormone

Receptors are a complex of protein structures designed to bind a hormone to elicit its cellular effects

usually found in the cell membrane or the nucleus.

Term for the increase/decrease of the number of receptors on target cells

An increase in the number of receptors on target cells is called up-regulationand a decrease is termed down-regulation.

Endocrine organs/glands that only exist to produce hormones

• Pituitary Gland

• Thyroid Gland

• Parathyroid Gland

• Adrenal Glands

what are “releasing hormones” & what synthesizes & releases them?

hypothalamus

released & stimulate the release of various hormones from the adenohypophysis (or anterior pituitary).

The main hormones produced and released by the hypothalamus are:

• Corticotropin Releasing Hormone or CRH

• Gonadotropin Releasing Hormone or GnRH

• Growth Hormone Releasing Hormone or GHRH

• Thyrotropin Releasing Hormone or TRH

also produces Oxytocin and Antidiuretic Hormone, but these are then stored and released by the neurohypophysis (or posterior pituitary)

What is the hypothalamus considered?

considered to be the crucial interface between the endocrine and nervous systems.

What does the Pituitary gland contain

contains hormones that generally affect the function of many organs in a variety of systems.

What are the two histologically distinct areas of the pituitary gland?

• Anterior lobe (or adenohypophysis) is made up of epithelial tissue

• Posterior lobe (or neurohypophysis) is made up of neural tissue

What does the anterior pituitary do?

produces a few different hormones:

• ACTH 

• FSH  and LH 

• GH

• TSH

• PRL

What does the posterior pituitary do?

produces NO hormones, it only stores and releases:

• Oxytocin

• ADH

hypothalamopituitary axis

structure that allows the hypothalamus and pituitary to interact

How do the hypothalamus and pituitary connect? And how is this structure formed?

a stalk called the infundibulum

There are cell bodies of neurons in the hypothalamus, their axons then form this infundibulum. 

What is the hypothalamohypophysial portal system

unique system of arterioles and capillaries associated with ghe infundibulum

Blood from a capillary network in the hypothalamus is able to flow through portal vessels into the glandular (anterior) portion of the pituitary.

Anterior Pituitary Hormones

• Adrenocorticotrophic Hormone (ACTH)

• LH & FSH

• Growth hormone (GH)

Adrenocorticotrophic Hormone (ACTH)

Hormone of the anterior pituitary

• Stimulates release of hormones from adrenal gland

• Corticosteroids (from adrenal cortex) are associated with "stress responses" and the fight or flight response

• Most organs have receptors for corticosteroids

LH & FSH

• Involved with the regulation of male and female reproductive processes (have receptors)

Growth Hormone (GH)

hormone of anterior pituitary

• Most organs, tissues, and cells within the body can respond to growth hormone

• Stimulates changes in target organs that support growth (mitosis, increased mobilization of nutrients, etc.)

Posterior Pituitary Hormones

• antidiuretic hormone (ADH

• oxytocin

Antidiuretic Hormone (ADH)

• Involved with kidney function (water retention)

Oxytocin

• Involved with smooth muscle contraction (uterus, myoepithelial cells in mammary gland)

What hormones does the thyroid gland release?

• Thyroid Hormones - T3 and T4

• Calcitonin - peptide hormone

T3 and T4

• tyrosine based, contain iodine

• T4 - Thyroxine

• T3 - Triiodothyronine

  • Increases basal metabolic rate - measure of oxygen use in resting conditions

  • Almost all tissues have receptors

• Ratio of T4 to T3 is 20:1

Calcitonin

• peptide hormone

• Helps control calcium levels

• Acts to decrease blood calcium by inhibiting osteoclasts

What does Parathyroid Gland release & how many do animals hv

• Most domestic animals have 2 pairs associated with the thyroid

• Secretes PTH

• increases osteocytes and osteoclasts

Parathyroid hormone (PTH)

• Increases blood calcium and lowers blood phosphorus

• Stimulates release of calcium and phosphorus from bone

Adrenal gland anatomy

divided up into the Adrenal Cortex (outer region)

& Adrenal Medulla (inner region)

The Adrenal Cortex produces:

• Glucocorticoids (cortisol and derivatives)

  • Enhances the production (or conversion) of glucose

• Mineralocorticoids (aldosterone)

  • Regulates sodium and potassium levels in the blood

The Adrenal Medulla produces:

• Catecholamines (epinephrine and norepinephrine)

  • Has a variety of functions in different organs but mostly prepares the animal for fight or flight

three main hormones produced by the Pancreas

• Insulin

• Glucagon

• Somatostatin

Insulin

Produced by beta cells

Decreases blood glucose

Describe the Control of Blood Glucose Levels & the types of diabetes

1. As you consume food, glucose is released into the bloodstream → blood glucose concentration to rise

2. insulin is released → lowers blood glucose by allowing cells to uptake glucose. The uptake of glucose provides energy to the cells.

3. Extra glucose will be stored as Glycogen in the liver, if blood sugar concentration drops too low, Glucagon causes the release of Glycogen which can be converted into glucose via the process of Glycogenesis.

Sometimes, there can be issues in the regulation of blood glucose levels, when this happens we have either Type 1 diabetes or Type 2 diabetes.

Type 1: the pancreas is unable to produce insulin;

• blood glucose levels too high

• there is a malfunction of the beta cells of the pancreas

Type 2: insulin insensitivity

• Insulin is produced in adequate amounts by the beta cells of the pancreas, but the body no longer responds to the insulin

• When the body no longer responds to the insulin, blood glucose levels become too high

Somatostatin

Slows the mobilization & production of nutrients

Somatostatin

Slows the mobilization & production of nutrients

The masses of endocrine tissue in the Pancreas are called the…

Pancreatic Islets (or Islets of Langerhans)

Pineal Gland location

located dorsocaudally in the Diencephalon

Pinealocytes

Cells of the pineal gland

neuronal & secretory

supported by neuroglia

receive input from axons

Pinealocytes manufacture an enzyme that converts serotonin to melatonin (hormone).

Melatonin

Pinealocytes manufacture an enzyme that converts serotonin to melatonin (hormone)

regulates the sleep-wake cycle (circadian rhythm). Melatonin peaks during darkness.

Hormones are regulated by two main methods:

negative feedback & positive feedback

Negative Feedback Regulation

• Rising levels of a hormone cause a biologic response to inhibit the further release

• Blood glucose levels

Positive Feedback Regulation

• less frequent than negative feedback

• Hormones cause a biologic response that produces an increase in the release of a hormone

• childbirth

What is the nervous system?

a network of billions of nerve cells linked together in a highly organized fashion to form the rapid control center of the body.

Functions of the nervous system

• Regulating the movement of body parts

• Regulating the secretion from glands

• Collecting information about external and internal environments

• Maintaining a state of consciousness

• Stimulating behavior for survival

In order for the nervous system to perform these functions it requires rapid transmission of information.

The nervous system has two major divisions:

Central

Peripheral