Lab 8 Vertebrate Anatomy Muscle and Organs- MAKE SURE TO MAKE A WHOLE SLIDE DEDICATED TO PICTURES

Attachments

• Tendons: muscle to bone

• Ligaments: bone to bone

Muscles consist of bundles of bundles

• Muscle: bundles of fascicles (covered by a layer of connective tissue called epimysium)

• Fascicle: bundles of muscle fibers (covered by a layer of connective tissue called perimysium)

• Muscle fiber: bundles of myofibrils (covered by a layer of connective tissue called endomysium)

  • skeletal (striated) muscle fibers consist of myofibrils (which are rows of sarcomeres)

    • this is not the case in smooth muscle, which has thin and thick filaments that don’t arrange into sarcomeres

• Myofibril: bundles of myofilaments; sarcomere level

• Myofilament (actin and myosin): interact to generate contraction of sarcomere

Muscle: Basic Histology

• Sarcomeres: the contractile units of a muscle bundle

• Sarcomere boundaries are Z disks (aka Z-lines) that hold thin filaments in position

  • in other words, a sarcomere is a region between 2 adjacent z-lines, containing thin actin filaments and thick myosin filaments

  • as a muscle is contracting, you’re bringing the two adjacent z-lines together (Z-disks are pulled together to shorten muscle and contract)

• The sarcomere’s M-line (middle) holds thick filaments in position

• Overlapping thick and thin filaments make up the A-band (dark) with the M-line in the center

• The area of the sarcomeres that only consist of thin filaments makes up the I-band (light) with the Z line in the middle

Muscle Actions (antagonist pairing)

• Extensors vs Flexors:

  • increase vs decrease joint angle

  • ex: quadriceps extend the knee, while hamstrings flex it

• Abductors vs Adductors:

  • away from vs toward the body’s midline

  • ex: pectoralis major adducts the arm

• Retractors vs Protractors:

  • move back vs move forward

• Supinators vs Pronators:

  • palm/sole anterior vs palm/sole posterior

Muscle Orientation

• Origin:

  • fixed end of the muscle

  • sometimes difficult to determine (i.e., back muscles)

  • the end closest to the midline of the body

  • Limbs: proximal, trunk: Medial

• Insertion:

  • portion that causes motion when muscle contracts

  • the end that is furthest from the midline of the body

  • Limbs: distal, trunk: Lateral

Anatomical Orientation

• Superior vs Inferior

  • closer to the head/upper part of the body vs closer to the feet/away from head

• Medial vs Lateral

  • toward the midline vs away from the midline of the body

• Proximal vs Distal

  • toward the origin or trunk of the body vs away from the origin or trunk

• Superficial vs Deep

  • closer to the body's surface vs away from the body's surface (closer to the body’s interior)

• Anterior = Ventral vs Posterior = Dorsal

  • the front of the body or structure vs the back

• Cranial vs Caudal

  • towards the head or skull vs towards the tail end of the body

• Frontal (coronal) Plane

  • divides the body into a front half and a back half

• Transverse Plane

  • divides the body into an upper half and lower half

• Sagittal Plane

  • dividing the body into a left section and a right section

Dorsal/Lateral Aspect Muscles

• The trapezius is divided into portions name for their different origins:

  • Clavotrapezius

  • Acromiotrapezius

  • Spinotrapezius

• The trapezius, spinodeltoideus, bicep brachii, latissimus dorsi cross the shoulder joint and move the arm

• External and internal obliques contain the abdomen

• Tensor fasciae latae, gluteus maximus, semitendinosus, and biceps femoris cross the hip joint to move the leg

• Gastrocnemius is the calf muscle that moves the foot

Ventral Aspect Muscles

• Sternohyoid muscle is used for swallowing

• Pectoralis major and pectoralis minor are parts of the same muscle with different origins that cross the shoulder joint

• Linea alba (white line) is connective tissue joining the right and left obliques

Organs

• Organs are composed of tissues that work together to perform a function

• The skin is our largest organ and is composed of each tissue type.

• The nervous system is also composed of all four types, primarily nervous

• note: in this lab, we are just focusing on the thoracic and abdominal organs

Body Cavities of Rat

• Thoracic cavity (upper)

• Abdominal cavity (lower)

Thoracic Organs of Rat

• Diaphragm separates thoracic and abdominal cavities and sits inferior to lungs

  • Function: primary muscle for breathing (inhalation and exhalation)

  • During inhalation, the diaphragm contracts and moves downward, expanding the thoracic cavity and lowering lung pressure, causing air to flow in

  • During exhalation, the diaphragm relaxes and moves upward, reducing thoracic cavity space and increasing lung pressure, pushing air out

• Heart is intermediate to the lungs (located between both lungs)

  • Right Atrium – receives deoxygenated blood from the body through veins and sends it to right ventricle

    Right Ventricle – pumps deoxygenated blood to the lungs to pick up oxygen

    Left Atrium – receives oxygenated blood from the lungs

    Left Ventricle – pumps oxygenated blood to the entire body through arteries

  • Myocardium = Heart Muscle

  • Pericardium = Membrane enclosing heart (fluid-filled sac that surrounds and protects the heart)

• Thymus gland superior to (above) heart

  • Function: immunity – it matures lymphocytes (which is important for fighting infections)

• The trachea (tube that carries air from the mouth/nose to the lungs) lies anterior to the esophagus (which carries food to the stomach)

  • Epiglottis: a flap that keeps food from entering trachea

  • Lined with cartilaginous rings anteriorly (reinforced to keep it from collapsing when breathing)

  • The trachea bifurcates (splits) at a structure called the carina into bronchial tubes, which enter lungs

    • bronchial tubes lead to bronchioles and then tiny alveoli, where gas exchange occurs → high surface area of the alveoli allows for efficient oxygen intake and CO₂ removal

  • Lungs have lobes – 4 in right lung of rat and 1 in the left lung

Abdominal Organs (located in the coelom- main body cavity)

• Esophagus (thoracic organ) leads to stomach (carries food to the stomach)

• The stomach breaks down food, begins protein digestion, and empties into the small intestine through the pyloric sphincter

  • Small intestine is divided into three sections: duodenum to jejunum to ileum, where digestion and absorption of nutrients

  • The pancreas releases digestive enzymes (and secretes insulin and glucagon, which regulate blood sugar levels)

  • The liver produces bile (digestion of fats)

    • Liver is composed of lobes, like the R lung

    • Aside from secreting bile, it also stores glucose as glycogen, filters toxins, and synthesizes macromolecules

    • Blood from the digestive system goes here to get cleaned before traveling back to the heart

• The ileum passes remnants of food into the colon (large intestine) through the ileocecal sphincter

  • The colon follows this path: cecum → ascending colon → transverse colon → descending colon → rectum → anus, where waste is processed and eliminated

• The spleen is located posterior and to the left of the stomach, and it filters and stores blood

Organ Coverings

• Body cavities are lined with membranes that provide protection, lubrication, and support

  • Visceral membrane: lines organs

  • Parietal membrane: lines the cavity wall

• Thoracic cavity:

  • Heart: covered by the pericardial membrane

  • Lungs: covered by the pleural membrane

• Abdominal cavity:

  • Peritoneal membrane: lines and protects the abdominal organs

  • Mesentery: connects organs to the body wall (holding them in place)

  • Omentum: connects organ to organ (providing cushioning)