Tutorial Lab 4 - Kingdom Animalia: Vertebrates

The skeleton of vertebrates is broadly divided into two parts

• 1) the axial skeleton consists of the skull, vertebrae and ribs

• 2) the appendicular skeleton consists of the pectoral and pelvic girdles and the bones of the appendages
  

The Axial Skeleton: SKULL

• The outer skull is an armor of dermal bone

• The inner skull is composed of endochondral bone

• Elements of the inner skull form the cranium or brain case

The Axial Skeleton: Vertebral Column

• A series of endochondral bones called vertebrae form the vertebral column.

• Vertebrae have several common features.

• The large spool-shaped central portion of each is the centrum
  

The Axial Skeleton: Vertebral Column

• Above the centrum, an arch of bone surrounds and protects the spinal cord.

• This is the neural arch.

• A dorsal projection, the neural spine, extends outward from the vertebral column

The Axial Skeleton: Vertebral Column

• The fish vertebral column is divided into two. subdivisions: the trunk and the tail (caudal).

• These vertebrae lack ribs. The rest of the trunk vertebrae possess ribs.

• Caudal (tail) vertebrae do not have ribs.

• They possess a ventral portion that forms a hemal arch, which surrounds blood vessels

• The neural arch with the neural spine is present in both trunk and tail vertebrae
  

The Appendicular Skeleton and Fins

• The Median Fins: The dorsal fins of the perch have fin rays for support.

• The anterior dorsal fin has ossified fin rays, which provide stiff support, while the fin rays of the posterior dorsal fin are not ossified and are flexible.

• Only the first two fin rays of the anal fin are ossified.

• The caudal fin is composed entirely of soft, unossified fin rays

The Appendicular Skeleton and Fins

• The Pectoral Girdle and Fins: The pectoral fins are attached to a bony girdle, the pectoral girdle.

• The pectoral girdle is composed of a number of fused elements.

• The girdle is also fused to the skull

The Appendicular Skeleton and Fins

• The Pelvic Girdle and Fins: The pelvic fins are attached to the pelvic girdle, which is composed of two bony pelvic plates.

• The plates may be fused along the midline.

• The pelvic girdle is not attached to the vertebral column or to the pectoral girdle, but is free floating (embedded in muscle only).

• Only the medial fin rays are bony, the rest are the typical soft unossified type

The Skin (Integumentary System)

• Skin is composed of two main layers; the outer epidermis overlaying the thicker dermis

• The epidermis in fish is relatively thin. Unicellular mucous glands are abundant in the epidermis.

• The dermis is composed of dense fibrous connective tissue and is attached to the underlying muscles by a layer of loose connective tissue.

• The scales of fish are located within the dermis

  
  
  

RAT AXIAL SKELETON SKULL

• mammals can breathe and chew food simultaneously because the nasal passages and the oral cavity (mouth) have been separated by a shelf of bone and soft tissue called the
  palate. Locate the following bones on a rat skeleton in the lab
  i) the tooth-bearing bones of the upper jaw  the maxilla and premaxilla;
  ii) the mandible;
  iii) the occipital
  

The Vertebral Column

• Vertebrae are divided into five groups (cervical, thoracic, lumbar, sacral and caudal)

The Vertebral Column

• The first cervical vertebra is the atlas and it articulates with the occipital condyles of the skull.

• Movement at this joint produces vertical movement of the head (the “yes” or nodding
  motion).

• The second vertebra is the axis Movement at the joint between the atlas and axis produces rotational movement of the head (shaking the head “no”)

The Vertebral Column

• Thoracic vertebrae bear ribs while lumbar vertebrae do not.

• Differentiation of trunk vertebrae into thoracic and lumbar regions is correlated with the evolution of a
  diaphragm. Most mammals have 12–15 thoracic and 4–7 lumbar vertebrae.

• The sacrum is formed by the fusion of 3–5 sacral vertebrae.

• Mammalian tails vary greatly in length and function and, therefore, the number and size of the caudal vertebrae varies between species

Sternum and Ribs

• As mentioned, differentiation of the trunk vertebrae into thoracic and lumbar regions is correlated with the evolution of a diaphragm.

• The diaphragm is a sheet of muscle that separates the thoracic cavity containing the lungs from the abdominal cavity

Sternum and Ribs

• The ribs help prevent the collapse of the pleural cavities when the diaphragm contracts and movement of the ribs occurs during deep or laboured breathing.

• All ribs attach dorsally to the thoracic vertebrae and curve ventrally.

• True ribs (7 pairs) attach directly to the sternum, while false ribs (3 pairs) attach to the rib(s) anterior to themselves.

• Floating ribs (3 pairs) do not have any ventral attachments.

• The sternum is formed by a number of elements. The clavicle of the pectoral girdle
  articulates with the first of these elements

Sternum and Ribs

• A xiphoid process composed of cartilage is
  attached to the last element - the xiphisternum.

• On the rat skeleton, locate the sternum,
  xiphisternum and all rib types

The Appendicular Skeleton

• The pentadactyl (five-digit) limb of terrestrial vertebrates evolved from fish fins. As tetrapod mammals adapted to land, their limbs became crucial for movement and body support.

• The basic vertebrate limb consists of three segments: one bone in the proximal part, two bones in the middle, and multiple bones with five digits in the distal part. All vertebrate limbs evolved from this common structure

Pectoral Girdle and Appendages

• Examine the rat skeleton and locate the bones forming the pectoral girdle.

• These are the scapulae (singular, scapula) and the clavicles. Next, locate the bones of the
  pectoral limb.

• In each pectoral limb there is a humerus in the upper portion, as well as a radius and ulna in the forearm region.

• The wrist consists of the carpals, while the palm
  of the hand is formed by the metacarpals. Finally, the digits are formed by phalanges.

Pelvic Girdle and Appendages

• Next, locate the bones of the pelvic limb.

• In each pelvic appendage there is a large femur in the thigh, as well as a tibia and fibula in the lower leg.

• The ankle consists of tarsals, and the main part of the foot is formed by metatarsals.

• As with the hand, the digits of the foot consist of
  phalanges.
  
  

The Skin (Integumentary System

• The epidermis in mammals is thick and has many layers of dead cells at the surface

• The dermis is composed of dense fibrous connective tissue and contains blood
  vessels, nerve fibres and sensory endings, arrector pili muscles, glands, and hair
  follicles

The Skin (Integumentary System

• Sebaceous glands and sweat glands are multicellular glands of epidermal origin.

• Sebaceous glands produce oily and waxy secretions that are usually secreted into
  hair follicles. Sweat glands occur in most, but not all mammals.

• The presence of hair is a distinct mammalian characteristic and hair is the most obvious derivative of mammalian skin
  

Reproductive System

• Note the circular outlines of the sections of seminiferous tubules, which are the site of sperm production.

• Also note mature sperm in the centers of some of these tubule

• Note the large sac-like follicles in which the ova (eggs) mature.

• When a follicle is ripe (Graafian follicle) and its ovum is mature, it bursts, releasing the ovum, which is then picked up by the oviduct.

The Arteries and Veins Of The Head

• The oxygenated blood leaves the left
  ventricle through the aortic semilunar valve and enters the aorta.

• The aorta immediately divides into the innominate artery and the aortic arch, which sends off two branches; the left common carotid artery and the left subclavian artery

• The aortic arch continues as the dorsal aorta
  

The Arteries and Veins Of The Head

• Locate the innominate artery and carefully trace its path cranially to the point at which it gives off two branches.

• The right common carotid artery is the branch which carries the blood to the right anterior portion of the head, and the right subclavian artery carries blood to the right front leg

• The venous system in the head region carries deoxygenated blood to the heart.

• The right and left superior venae cavae, which you located in the Practical lab, are parts of this system

The Visceral Arteries and Veins

• Numerous intercostal arteries arise from the
  dorsal aorta and go to the ribs. Just posterior to the diaphragm, the first large unpaired
  abdominal artery that branches from the aorta is visible.

• This is the coeliac artery

The Visceral Arteries and Veins

• After a short distance, the coeliac artery gives rise to three smaller arteries: the splenic, hepatic, and gastric arteries

• The second unpaired branch of the dorsal aorta is the superior mesenteric artery

• Locate the paired renal arteries, which come off the aorta after the superior mesenteric artery and carry blood to the right and left kidneys

The Visceral Arteries and Veins

• Just posterior to the renal arteries are the small paired ovarian arteries (female) or testicular arteries (male) which supply blood to the ovaries or testes

• In the same region, locate the two iliolumbar arteries which branch off the aorta and carry blood to the dorsal body wall.

• Also in the region of the iliolumbar arteries, the dorsal aorta gives off the inferior mesenteric artery, which carries blood to the colon and rectum

The Visceral Arteries and Veins

• The dorsal aorta then splits into two branches, the left and right common iliac arteries, which divide into a number of branches supplying blood to the reproductive organs and hind limbs.

• From the branching of the common iliac arteries, the dorsal aorta is known as the caudal artery which supplies blood to the tail

The Visceral Arteries and Veins

• In many instances, the venous system has comparable blood vessels to that of the
  arterial system

• Starting near the caudal end, locate the left and
  right common iliac veins, which flow into the inferior vena cava
  

The Visceral Arteries and Veins

• Trace the inferior vena cava and note that as it runs anteriorly several veins flow into it, including the paired iliolumbar veins, testicular veins (male), ovarian veins (female), and the renal
  veins

The Visceral Arteries and Veins

• Each of these are visible next to the artery of the same name.

• The inferior vena cava eventually enters the liver where the hepatic vein enters it.

• This is usually buried deep within the liver tissue and is not visible.

• The inferior vena cava then continues on to
  enter the right atrium