Cat Anatomy for Cat Owners

Cat Posture

Humans are bipeds because they walk on their two feet, while cats are quadrupeds because they walk on all four legs. Humans have a plantigrade foot posture, which means that the surface of our whole foot touches the ground during locomotion.

Cats, on the other hand, are digitigrade, which means that only their phalanges (their toes and fingers)touch the ground when they walk, while their ankles and wrists stay elevated. Look at the picture below to see the differences and similarities in hand and foot anatomy between cats and humans. You can see that the cat’s foot bone varies greatly from a human’s.

Source – Merck Veterinary Manual

See an image of this here Source

See an image of this here Source

Anatomy of the Paw

Basic cat anatomy, cats have 18 toes. They have 4 toes and one dewclaw on each of their front legs, and 4 toes on each of their hind legs. The dewclaw is a rudimentary toe and it does not contribute to the cat’s posture, as it does not walk on it, it remains elevated when the catwalks.

Cats have skin pads on the inner part of their paws, which are adapted for walking. They are tough enough to support the cat as it walks on rough surfaces, but they also have a sensory role, which means that they are sensitive to several signals like hot, cold, pain, and the texture of the ground. They have several groups of pads:

Fore Legs

• 5 digital pads – one for every toe, including the dewclaw, which has a smaller digital pad
• 1 metacarpal pad – this is much larger than the other pads because it supports the main weight-bearing leg bones – the metacarpal bones
• 1 carpal pad – this pad is smaller than the digital paws, and it supports the cat’s wrist bone

Hind Legs

• 4 digital pads – one for each toe
• 1 metatarsal pad – of similar size to the metacarpal pad and which supports the cat’s metatarsal bones

Anatomy of the Claw

Cats have retractable claws on both their front and rear paws. They keep their claws retracted when they are relaxed, and they can control when to extend their claws and use them. Their use ranges from simple actions like scratching an itch to complex ones like self-defense or hunting. Cats also use their claws for extra traction when they climb up. As any cat owner knows very well, cats sharpen their claws regularly.  

See an image of this here Source – Encyclopaedia Britannica

Cat claws’ anatomy is similar to human nails, they are resistant to keratinous plates. Underneath the keratinous potion found at the tip of the claw, there are tiny blood vessels that feed the claw and keep it growing. The sheath is located at the base of the claw and has a protective role. When cutting a cat’s claws, you must be very attentive not to cut too high. Cutting the quick results in a hemorrhagic episode.   

Read our Guide to Trimming Your Cat’s Nails

Anatomy of the Ear

Cats have excellent hearing. They can detect sounds in a range of frequencies that is both above and below the human range, which means that they can hear better than people do. Cats also have better hearing than dogs. Aside from hearing, the ear is also an organ of balance. The ear consists of the outer, middle, and inner ear.

Source – Merck Veterinary Manual

The Outer Ear – includes the pinna, which is the visible part made out of cartilage and covered by skin and fur, and the external auditory canal. The pinna is cup-shaped to capture sound waves and funnel them towards the inner ear through the auditory canal and finally to the eardrum. As opposed to humans, cats have mobility in their outer ears, which they can also move independently of each other. Another difference from the human ear is that cats have a deeper and more tapered ear canal, which contributes to their superior hearing because it creates a better funnel to carry sound.

The Middle Ear – includes the eardrum and a small chamber containing 3-minute bones – the hammer, the anvil, and the stirrup. There are also 2 muscles – the oval window and the eustachian tube – this small muscular tube connects the ear with the back of the nose and its role is to permit air to pass to the ear).

The Inner Ear – includes the cochlea, which is a hearing organ, and the vestibular system, which is the organ of balance. This is a complex structure including semicircular canals filled with fluid which have a very important role in balance. Compared to the human inner ear, the cat is more developed because they also have superior balance. Read more about the anatomy of these complex structures.

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Anatomy of the Eye

Cat eyes function similarly to human eyes and cats can have many of the eye problems that people have – like glaucoma and cataracts. Cats, however, display increased eyesight acuity to help them be effective hunters. They can see much better than humans can in the distance and they can see clearly in dim and almost no light. Cats, however, can’t see objects located closely very clearly. They use their whiskers to help them discern objects that are very close to them.

Find out more about How Whiskers Work in our Article

Cats have slit-like pupils, which contract in bright light to let very little light in, and dilate in low light to permit as much as possible to come in. Their pupils are very versatile, they can contract up to the point where they become a barely visible strip, and they can dilate to the point where they become circular.

The cat has an upper eyelid and a lower eyelid, both with eyelashes, but it also has a third eyelid called the nictitating membrane. This is aimed to protect the cat’s eye from rough particles like sand or from scratches when the cat is, for instance, traveling through a bush. The nictitating membrane is a white-pinkish pellicle, which is visible at the inner edge of the eye, and which closes from the inner edge towards the outer edge of the eye.

Cat owners usually don’t notice the nictitating membrane because house cats usually don’t need to use it. It becomes visible, though, should it become inflamed, when it swells up. The inflammation of the third eyelid is called “cherry eye” because the swelled membrane looks like a small red cherry located towards the inner edge of the eye.

Source – Merck Veterinary Manual

See an image of this here Source – Veterinaryhub

Skeleton Anatomy of the Cat

Source – Lumen – Atlas of Comparative Vertebrate Anatomy

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From The Merck Veterinary Manual, online version. Scott Line, ed. Copyright © 2020 by Merck & Co., Inc., Kenilworth, NJ. All rights reserved. Used with permission. Available at: www.MerckVetManual.com. Accessed December 10, 2020

The cat’s skeleton is adapted to be very flexible.  They have no collarbone and they have a very limber backbone with 7 cervical vertebrae, 13 thoracic vertebrae (that’s one more than humans have), 7 lumbar vertebrae, 3 sacral vertebrae (that’s 2 less than humans – humans have 5 sacral vertebrae because they have bipedal posture), and 22-23 caudal vertebrae (humans have 3-5 caudal vertebrae, which form the coccyx – this a rudimentary bone from our ancestors who had tails). Please note that the number of caudal vertebrae differs among the various cat breeds according to the length of the tail. Manx cats, for instance, have no tails at all, while bobtail cats have short tails and an average of 15.8 vertebrae.

The increased flexibility and mobility that cats have in their spine comes from the extra lumbar and thoracic vertebrae (compared to humans), as well as their tails, which cats use to counterbalance their bodies during quick movements. Their vertebrae are also adapted to support shocks and cushion their jump landings – they have elastic discs between every two vertebrae.

Anatomy of the Digestive System

The digestive system begins at the mouth and it continues with the esophagus, the stomach, the liver, the pancreas, the intestines, the rectum, and, finally, the anus. Cats are carnivores and their digestive system is adapted for processing meat.

Dental Anatomy of Cats

Cats have very small incisors – the central, intermediate, and lateral incisor on each side, so 6 incisors on the maxilla (the upper jaw) and six on the mandible (the lower jaw), followed by very sharp canines, which are adapted for hunting – they are used to grasp and tear. Cats have two large canine teeth on the maxilla and two on the mandible and the lower canine intersects with the upper lateral incisor and the upper canine.

The canines are followed by the premolars, which have sharp edges and are adapted for shredding, and then by the molars, which cats use for grinding. Cats have three 3 premolars on each side of the maxilla and 2 premolars on each side of the mandible. They have 1 molar on each side, on both the maxilla and the mandible.

Source – Merck Veterinary Manual

From The Merck Veterinary Manual, online version. Scott Line, ed. Copyright © 2020 by Merck & Co., Inc., Kenilworth, NJ. All rights reserved. Used with permission. Available at: www.MerckVetManual.com. Accessed December 10, 2020

Find out more about Dental Anatomy and the Basics of Veterinary Dentistry

Cats have papillae on their tongues, which are sharp spines that they use to rip the flesh off of their prey, but also to groom themselves. The papillae are keratin-based and they are shaped like small backward-facing hooks. Cats have increased mobility in their tongue, which they use for grooming and drinking water.

See an image of this here Source – Wikipedia  

Digestion begins in the mouth when the cat grabs and chews its food. Saliva is rich in enzymes that kick-start the digestion process. The cat swallows the food, which is minced and mixed with saliva, and it goes through the esophagus to the stomach. There, it is mixed with gastric juice (gastric acid or stomach acid) which breaks the substances in the food. Cats have highly acidic gastric juice to digest their meat-based diet.  The stomach also has a role in absorbing nutrients.

After the food is digested in the stomach, it passes to the first part of the small intestine, the duodenum, where the digestive process continues. In the duodenum, the food is mixed with bile, which is produced by the liver and stored in the gallbladder. Bile emulsifies fat (it has a crucial role in fat digestion) and neutralizes the acid PH of the partially-digested food coming from the stomach. It is also in the duodenum where the food is mixed with pancreatic juice, produced by the pancreas and rich in enzymes that help break down the nutrients so that they can be absorbed by the intestinal mucosa.

The food then passes to the jejunum, which is adapted to absorb nutrients. The liver regulates the level of nutrient absorption from the small intestine in the bloodstream. The food then passes to the third portion of the small intestine – the ileum, which is connected to the large intestine.

Source – Merck Veterinary Manual

The large intestine has 4 portions – the cecum, the colon (compartmentalized into ascending, transverse, and descending colon – each of the three portions has a different role), the rectum, and the anal canal. Its main role is to absorb water and electrolytes from the food and form fecal matter, which is then ejected through the anal canal.

For more images, take a look at Vetcheck

Anatomy of the Respiratory System

The cat’s respiratory system consists of large and small airways and the lungs. When hunting, cats need to take in large amounts of oxygen, which is why they have long airways. Cats can breathe in through their noses and their mouths.

Source – Merck Veterinary Manual

The air then travels down the trachea, which has a tubular shape and is made out of tracheal cartilages connected via annular ligaments. The trachea then branches into two tubes, the left, and right bronchi, which enter the lungs at the hilum.  The primary bronchi, in turn, branch into smaller tubes called bronchioles in the lungs. The tubes become smaller and smaller (forming the bronchial tree) and finally end with alveoli, which are small sacs where the barrier between the air and the blood is a thin membrane, allowing the oxygen to pass into the blood. The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during breathing.

See an image of this here Source – Wikipedia

See an image of this here Source – Wikipedia

For more images of the cat’s respiratory system, take a look at this atlas from Washington State University  

Anatomy of the Urinary Tract

The upper urinary tract comprises the kidneys and the ureters. Out of each kidney, one ureter emerges, which is a muscular tube that connects the kidney to the urinary bladder and that transports urine. The lower urinary tract consists of the urinary bladder and the urethra.

The main role of the urinary system is to eliminate waste products resulting in the process of transforming food into energy in the form of urine. Its secondary role is to maintain the correct balance of water and electrolytes in the body. The urinary system also has a third role, which is metabolic. It produces erythropoietin and renin – which are used for producing blood cells and other roles, and it also processes vitamin D.

The kidneys are palpable during physical examination in cats. Compared to dogs, cats have mobile kidneys. They are retroperitoneal structures that are located along the caudal border of the ribs at the midline. They are approximately 4-5 cm long and they are firm and smooth on palpation.  Please note that in overweight cats, palpating the kidneys may not be possible.

Cat Bladder Anatomy – Source –Merck Veterinary Manual

Source –Merck Veterinary Manual

Find more images in this veterinary anatomy atlas from Washington State University

Anatomy of the Genital System

In females, the genital tract consists of the vulva, the vagina, the uterus, the oviducts or Fallopian tubes, and the ovaries. The uterus is separated from the vagina by the cervix, which also serves as a protective barrier against infection passing from the vagina to the uterus. The uterus has 2 uterine horns and it is adapted to cats birthing carrying several kittens in a pregnancy. The Fallopian tubes are connected to the ovaries and the uterus. After ovulation, the mature eggs are transported through these tubes to the uterus.

Source – Merck Veterinary Manual

Source – Merck Veterinary Manual

Source – Merck Veterinary Manual

In males, the genital tract consists of the testicles, where sperm is produced, and then transported via the epididymis and the ductus deferens to the urethra. The sperms are stored in the epididymis, where they mature. The accessory sex glands, such as the prostate, produce the fluid part of semen. The cat’s penis has small keratinous spines on its surface. This is an adaptation to reproduction in the wild which cats get from large felines. In the wild, one female typically mates with several males. The main role of the spines on the male’s penis is to clean the female’s urinary canal of other males’ sperm and ensure that theirs is the one that produces the offspring.  

See an image of this here Source – Wikipedia

The cat anatomy is complex. To find out more about it, please use the resources below:

• Cat Anatomy and Physiology from Washington State University
• Veterinary Anatomy Dictionary
• Vetcheck – Cat Anatomy
• Cat Anatomy – Washington State University
• Merck Veterinary Manual