Experiments on the appearance and anatomy of rabbits
Experiments on the appearance and anatomy of rabbits
Source of content: general zoology lab guide.
Operation method
Experiments on the appearance and anatomy of rabbits
Principle
1. to acquire the main characteristics of mammals through observations of the appearance and anatomy of the domestic rabbit; 2. to recognize and summarize the progressive characteristics of the mammalian skeletal system as adapted to terrestrial life.
Materials and Instruments
specimens Move This experiment should begin with observation of the whole skeletal specimen of the rabbit, distinguishing its central axial skeleton, band bones and limb bones, and understanding their basic composition and general parts. Then carefully identify the main bones of each part and grasp their important adaptive features. Caveat Take care to protect the skeletal specimens by not marking the bone joints, etc., with pencils, etc.; do not damage the natural interconnections between the bone fragments. Common Problems I. Demonstration 1. skull specimens of different types of mammals, e.g. insectivores, carnivores, primates, odd-toed ungulates, even-toed ungulates, etc., with attention to comparing and summarizing the characteristics of the skulls of the various groups of animals. For more product details, please visit Aladdin Scientific website.
Dissectors Magnifiers
I. Observation of appearance
The body surface of the rabbit is covered with hair. There are 3 types of hairs, i.e., needle hairs, downy hairs and tactile hairs. Needle hairs are sparse, thick and long, with hair direction; downy hairs are fine, short and dense, without hair direction; tactile hairs, or whiskers, are attached to the side of the mouth, long and hard, with sensory functions.
The body of the rabbit is divided into 4 parts: head, neck, trunk and tail. Carefully identify the relevant structures of each part.
II. Skeletal System
1. Axial skeleton: The axial skeleton of the rabbit consists of the spine, thorax and skull.
Spine: The spine of the rabbit consists of about 46 vertebrae. It can be divided into 5 parts, i.e. cervical, thoracic, lumbar, sacrum and caudal vertebrae.
Taking the 1 detached thoracic vertebrae as a representative, note the structure of the parts below the vertebrae:
(1) Vertebrae: The vertebrae of mammals are biplane and short columnar, which can withstand greater pressure. The vertebrae have flexible intervertebral discs between them.
(2) Arch: A bow-shaped piece of bone located dorsal to the vertebrae, the inner cavity of which houses the spinal cord.
(3) Vertebral spine: The central protrusion in the dorsal center of the vertebral arch that serves as the attachment point for the dorsal muscles.
(4) Transverse process and articular process: The transverse process is the lateral projection of the vertebral arch, which has an anterior and posterior articular process in front of and behind it, and is associated with the articular process of the neighboring vertebrae.
(5) Articular facets of the ribs: The transverse processes of the thoracic vertebrae have articular facets at the end of the transverse processes that are articulated with the costal nodes. The vertebrae of the neighboring vertebrae together form an articular surface associated with the tuberosity of the ribs. Thus there is a double connection between the ribs and the vertebrae.
Thoracic vertebrae: characterized by high dorsal vertebral spines, ventrally connected to the ribs.
Lumbar vertebrae: 12 to 15. They appear to be the most robust of the vertebrae. The transverse processes reach and point obliquely anteriorly and inferiorly.
Proprioception: It consists of 4 vertebrae, which form the healing propodeum. The sphenoid bone is connected to the girdle by a broad articulating surface (try to recall the sphenoid vertebrae of frogs and reptiles, and understand the significance of changes in the number and shape of the sphenoid vertebrae for terrestrial life).
Caudal vertebrae: 15-16 vertebrae. The front several caudal vertebrae have vertebral canals to accommodate the terminal filaments of the spinal cord; the rear caudal vertebrae have only vertebral bodies and are cylindrical in shape.
Thorax: The thorax consists of thoracic vertebrae, ribs and sternum. There are 12-13 pairs of ribs in rabbits, the first 7 pairs directly connected to the sternum are true ribs; the rear ones not directly connected to the sternum are false ribs. When a rib is taken from the front of the thoracic vertebrae, it can be seen that the upper part of the bony rib is connected with the thoracic vertebrae through two joints, and the lower part is connected with the sternum through cartilage.
The sternum constitutes the base of the thorax and consists of 6 bones. The most anterior one is the sternal pedicle; the most posterior one is associated with a cartilaginous plate called the raphe; the sternal bones located between the sternal pedicle and the raphe are collectively referred to as the sternal body.
Skull: The mammalian skull has a reduced number of bone fragments and a high degree of healing. Take a skull specimen and observe it in sequence from posterior to anterior against the illustrations in the textbook:
(1) Posterior
The occipital bone surrounds the foramen magnum of the occipital bone, which is formed by the fusion of the basioccipital bone, the supraoccipital bone, and the left and right external occipital bones. There is an occipital condyle on each side of the occipital bone, which is associated with the atlas. The foramen magnum is the pathway between the spinal cord and the medulla oblongata.
(2) Upper part
It consists of the interparietal bone, parietal bone, frontal bone and nasal bone from back to front. The interparietal bone is located in the anterior center of the upper occipital bone and is connected to one pair of parietal bones. In rabbits, the interparietal bones are small. The parietal, frontal and nasal bones are paired lamellae. The nasal bones are long and the cavity they cover is the nasal cavity. The opening at the anterior end is the external nostril.
(3) Bottom
From back to front, they are the base of the occipital bone (basioccipital bone), basal pterygoid, anterior pterygoid (with pterygoid protuberances on both sides), palatine bone, maxilla and premaxilla. The basal pterygoid is triangular in shape and lies anterior to the basioccipital bone. The anterior pterygoid is elongated and lies in the center of the anterior ventral surface of the basipterygoid. The palatine bones are located on either side of the anterior pterygoid, which meets the maxilla anteriorly.
Note the observation of the bony secondary palate
(4) Lateral
A large piece of bone called the temporal bone is visible anterior to the external occipital bone. It is a composite bone formed by the healing of the squamosal bone, the olecranon (the rocky part of the temporal bone, which is only visible in a sagittally cut skull), and the tympanic bone.
(5) Mandible
It consists of a single odontoid bone. There is an articulating surface on its ascending branch and a joint associated with the temporal bone.
What are the structural similarities and differences between the skull of a cat as compared to that of a rabbit? Based on your observations, write their respective dentition patterns.
2. Girdle and limb bones: Observations on the girdle bones will be the main focus.
(1) Shoulder girdle and forelimb bones
The shoulder girdle consists of the scapula and clavicle.
The forelimb bones consist of the humerus, radius, ulna, carpal bones, metacarpals and phalanges.
(2) Girdle and hind limb bones
The lumbar girdle consists of the ilium, sciatica, and pubic bone fused into the unnamed bone.
The hind limb bones are composed of femur, tibia, fibula, tarsus, paternosterone and phalanges. The tibia is larger and longer than the fibula. In addition, there is a kneecap at the lower end of the femur.
Digestive System
Execution of experimental animals: Place the rabbit in a dissecting tray or on the floor of the laboratory, insert a needle into the marginal vein of the ear, inject 10mL of air, and the rabbit will die within a few minutes. Be careful to inject from the distal end of the marginal ear vein. Live rabbits can also be killed by ether fumigation or neck-breaking.
Anatomy: Take the rabbit executed by neck-breaking and place it on its back in a dissecting disk. Fix the limbs with a string, moisten the hair on the midline of the abdomen with cotton dipped in water, then lift the skin from the genital opening slightly in front, and cut the skin longitudinally along the midline of the abdomen from back to front until it reaches the bottom of the lower jaw. The skin was then cut horizontally from the nape of the neck to the left and right to the base of the auricle. The edges of the cut skin at the neck were picked up with forceps held in the left hand, and the subcutaneous connective tissue was carefully removed with a scalpel in the right hand. Observations were made in the following order:
1. Salivary glands: Rabbits have four pairs of salivary glands
(1) Parotid glands (subauricular glands): they are located ventrally in front of the base of the ear shell, immediately under the skin, and can be seen by peeling back the skin. The parotid glands are irregular, light red glands with irregular shapes, and their ducts open at the floor of the mouth (no need to look for them).
(2) Submaxillary glands: located on both sides of the ventral surface of the posterior part of the mandible, they are a pair of ovoid glands. The ducts open at the floor of the mouth (no need to look for them).
(3) Sublingual glands: located just outside and above the right and left submandibular glands, they are small and yellowish in color. The sublingual glands, which are nearly round, can be seen by removing the nearby lymph nodes (round). A pair of sublingual gland ducts protrudes from the medial side of the gland, and the accompanying sublingual gland ducts open into the floor of the oral cavity.
(4) Suborbital gland: located anteriorly and inferiorly at the base of the eye socket, pink in color.
2. Oral cavity
The oral cavity is fully uncovered by cutting the buccal region along the corner of the mouth, removing the masticatory muscles on one side, and using bone scissors to open the joints of the mandible and skull on that side.
The anterior walls of the mouth are the upper and lower lips, the lateral walls are the cheeks, the upper wall is the palate, and the lower wall is the floor of the mouth. The front of the mouth between the teeth and the lips is the vestibule. The 2 pairs of long, chiseled teeth located at the most anterior end are incisors; behind them are each of the 3 pairs of short, broad, and abrasive premolars and molars.
At the anterior end of the roof of the mouth, the hard palate can be felt with the hand; at the posterior end is the soft palate. The hard palate and soft palate form the nasal access. The floor of the mouth has well-developed fleshy lips. The tongue is attached to the floor of the mouth by an anterior ventral tether. The surface of the tongue has numerous small papillae with taste buds on them. The base of the tongue has a single contouring papilla.
3. Pharynx
The pharynx is located on the dorsal surface behind the soft palate. The aperture formed by the free edge of the soft palate is the isthmus of the pharynx.
The cavity exposed by cutting along the midline of the soft palate is the nasopharyngeal cavity, which is part of the pharynx.
At the anterior end of the nasopharyngeal cavity is the endonasal aperture. In the lateral wall of the nasopharyngeal cavity is 1 pair of oblique fissures is the opening of the Eustachian tube.
If probed with a pig's mane, this tube leads to the middle ear cavity. The pharynx tapers posteriorly and connects to the esophagus. Anterior to the esophagus is the entrance to the respiratory tract. Here there is a lobe-shaped protrusion called the epiglottis (located at the base of the tongue).
The esophageal passage and the gas passage cross at the back of the pharynx, and the epiglottis prevents food from entering the airway.
4. Larynx, Trachea and Lungs
(1) Larynx
The muscles of the ventral surface of the neck are removed for visualization. The larynx is a cavity composed of cartilage. There is a large opening at the tip of the larynx known as the glottis. There is an epiglottis at the dorsal margin of the larynx. On the dorsal surface of the epiglottis is the opening of the esophagus. The large shield-shaped cartilage on the ventral surface of the larynx is the thyroid cartilage. The cricoid cartilage surrounds the larynx posteriorly. The dorsal surface of the cricoid cartilage is wider and has 1 pair of small projections as the spoon-like cartilage. The folds on the inner wall of the laryngeal cavity are the vocal cords.
In order to continue the observation the muscles at the back of the neck have to be cut and the thoracic cavity opened. The internal structure of the thoracic cavity can be observed by removing the sternum by cutting the ribs with bone scissors.
(2) Trachea
The trachea extends backward from the larynx, and its wall is supported by many cartilaginous rings, the back of which is incomplete and is close to the esophagus. The trachea extends backward into 2 branches into the lungs. On each side of the cricoid cartilage is a flat oval gland called the thyroid gland.
(3) Lungs
The trachea enters the thoracic cavity and divides into 2 branches into the lungs. Each branch is connected to the base of the lungs. The lungs are spongy organs located in the thoracic cavity on either side of the heart.
5. Alimentary canal and digestive glands
(1) Alimentary canal
Esophagus: located at the back of the trachea, it extends posteriorly from the pharynx into the thoracic cavity, crosses the diaphragm and enters the abdominal cavity to connect with the stomach.
Stomach: an enlarged sac, partly covered by the liver. The esophagus opens in the middle of the stomach. The stomach is connected to the esophagus by the cardia; to the duodenum by the pylorus. The stomach is divided into two parts: the left gastric wall is thin, transparent and grayish-white, with mucous glands on the mucous membrane; the right gastric wall is reddish-gray because of its thicker muscular texture and more blood vessels. The mucous membrane is covered with longitudinal ribs and glands capable of secreting gastric juice. On the lower left side of the stomach there is a dark red striped gland for the spleen. It is a lymph gland.
Intestinal Tube: The thin, coiled anterior portion of the intestinal tube is the small intestine; the posterior portion is the large intestine. The small intestine is subdivided into the duodenum, jejunum, and ileum; the large intestine is divided into the colon and rectum. At the junction of the small and large intestines is the cecum. The duodenum, after the pylorus of the stomach, curves and travels to the right, with the common hepatic duct injecting on the side close to the liver. On its opposite side there is the pancreatic duct injected. The jejunum and ileum are not distinct in appearance. The posterior end of the duodenum is the jejunum and then the ileum. The cecum is the blind sac between the junction of the small and large intestine. The cecum is more developed in herbivores; it is reduced in carnivores. The colon has a longitudinal band of muscle fibers that tighten the intestinal tube into a ring, hence the name colon. The colon is divided into three parts: the ascending colon, the transverse colon, and the descending colon, which can be distinguished by their natural position. The last end of the large intestine is the very short rectum, which opens into the anus.
(2) Digestive glands
The salivary glands described earlier are also digestive glands. The following are the digestive glands that are located outside the alimentary canal and are connected to the alimentary canal by ducts.
Liver: It is the largest digestive gland in the body and is located in the anterior part of the abdominal cavity and is dark red in color. It is divided into 6 lobes, i.e., left outer lobe, left middle lobe, right middle lobe, right outer lobe, square lobe and caudate lobe. Between the caudate lobe and the right external lobe there is a pathway of arteries, veins, nerves and lymphatics called the porta hepatis. In rabbits, the gallbladder is located dorsal to the right middle lobe of the liver, and bile enters the duodenum along the bile duct.
Pancreas: Scattered in the bend of the duodenum, it is a multibranched yellowish gland. One (several in rats) pancreatic duct opens into the duodenum and does not need to be searched for in detail.
IV. Excretory system
1. Excretory system
The kidneys are purplish-red bean-shaped structures.
It is located at the back of the abdominal cavity and is tightly attached to the body wall by a tethered membrane. It is connected to the bladder by a white ureter. There is a small round adrenal gland (endocrine gland) in front of the kidney. Urine passes through the bladder to connect to the urethra, which opens directly outside the body. Cut off one side of the kidney.
Dissect it along the side, rinse it with water and observe: the peripheral part is the cortical part and the inner part with a radial texture is the medullary part. The cavity in the center of the kidney is the renal pelvis. From the medulla there is a papillary projection into the renal pelvis. Urine passes through the papilla into the renal pelvis and then through the ureter into the dorsal part of the bladder. 2. Reproductive system
Male and female specimens can be observed interactively after dissection.
(1) Male
The testes are 1 pair of white, ovoid organs.
They descend into the scrotum during the breeding season; during the non-breeding season they are retracted into the abdominal cavity. The scrotum is open to the abdominal cavity by a groin canal orifice. The coiled tubular structure at the end of the testis is the paratestis. The white tube extending from the paratestis is the vas deferens. The vas deferens enters the penis through the back of the bladder and passes outside the body. On the ventral surface of the vas deferens at its junction with the bladder, there is a pair of cockle-shaped seminal vesicle glands. A transverse section of the penis reveals a centrally located urethra, which is surrounded by two blood vessel-rich corpus cavernosum.
(2) Female
The purple-yellow glands with granular projections above the kidneys are the ovaries.
There is a thin oviduct on each side of the ovary. The oviducts open into the abdominal cavity by means of a trumpet at the end. The inflated lower part of the oviduct is the uterus. Some specimens show small embryos or absorbed "uterine spots" (purple blotches) in the uterus. The uterus is united on both sides in a "V" shape and opens out of the body through the vagina.
How do the anal, urethral, and genital openings of females and males differ?