Human Anatomy: A Comprehensive Guide to the Body’s Systems and Functions
Dental Formula
Definition-The term definition is mainly used to describe the arrangement of teeth, including their number and types. A normal adult has 32 teeth. Animals have different types and shapes of teeth, which are specialized based on Nutrition in animals or their eating habits.
What is a Dental Formula?
The method of expressing or describing the total number of teeth in man and animals according to the arrangement is termed as the Dental Formula. This formula is expressed using letters and figures. The letters used in this formula are based on the 4 types of teeth like- Incisor, Canine, Premolar, and Molar.
The Dental Formula is expressed as: (The number of each type of teeth in the upper jaw)/(The number of teeth on one side of the lower jaw)
Dental Formula =
(2 incisors 1 canine 2 premolar 3 molar) / (2 incisors 1 canine 2 premolar 3 molar)
Humans have two dental formulae:
The primary dentition (20 teeth):
12/2 C1/1 M2/2 = 10
The permanent dentition (32 teeth):
12/2C1/1 P2/2 M 3/3 = 16.
Where: I – Incisors, C-Canine and M-Molar
Among all other mammals, both humans and apes have similar sets of teeth and dental formulae.
Micturition
or urination is the process of emptying urine from the storage organ, namely, the urinary bladder. The detrusor is the smooth or involuntary muscle of the bladder wall. The urethral muscles consist of the external and internal sphincter. The internal sphincter and detrusor muscle are both under autonomic control. The external sphincter, however, is a voluntary muscle under the control of voluntary nerves.
The bladder normally accommodates up to 300- 400 ml in adults. When the bladder is distended it sends signals to the brain, which is perceived as the ‘full bladder’ sensation.
The process of emptying the urine into the urethra is regulated by nervous signals, both from the somatic and the autonomic nervous system. The autonomic nervous system comprises both the sympathetic and the parasympathetic nervous system.
The bladder has two states of function; the storage and emptying phases.
Structure and function of human kidney
■Remove waste products and medicines from the body
■Balance the body’s fluids
■Balance a variety of electrolytes
■Release hormones to control blood pressure
■Release a hormone to control red blood cell production
■Help with bone health by controlling calcium and phosphorus
What is Nephron?
A nephron is the basic structural and functional unit of the kidney. They are the microscopic structure composed of a renal corpuscle and a renal tubule. The word nephron is derived from the Greek word – nephrons, meaning kidney. There are about millions of nephrons in each human kidney.
Structure of Nephron
The mammalian nephron is a long tube-like structure, its length varying from 35-55 mm long. At one end, the tube is closed, folded and expanded, into a double-walled, a cuplike structure called the Bowman’s capsule or renal corpuscular capsule, which encloses a cluster of microscopic blood vessels called the glomerulus. This capsule and glomerulus together constitute the renal corpuscle.
The structure of nephron comprises two major portions:
1. Renal Tubule 2. Renal Corpuscle
Renal Tubule
The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function.
• The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus; it stays in the renal cortex.
• The second part is called the loop of Henle, or nephritic loop because it forms a loop (with descending and ascending limbs) that goes through the renal medulla.
• The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex.
Renal Corpuscle
The renal corpuscle consists of a glomerulus surrounded by a Bowman’s capsule. The glomerulus arises from an afferent arteriole and empties into an efferent arteriole. The smaller diameter of an efferent arteriole helps to maintain high blood pressure in the glomerulus.
The Bowman’s capsule is divided into three layers:
1. Outer Parietal layer: It is made up of epithelial cells with minute pores of diameter 12nm.
2. Middle Basement membrane: This layer is selectively permeable.
3. Inner Visceral Layer: It consists of large nucleated cells called podocytes which bear finger-like projections called podocel.
What is the renin-angiotensin- aldosterone system (RAAS)?
The renin-angiotensin-aldosterone system (RAAS) is the system of hormones, proteins, enzymes and reactions that regulate your blood pressure and blood volume on a long-term basis.
It regulates your blood pressure by increasing sodium (salt) reabsorption, water reabsorption (retention) and vascular tone (the degree to which your blood vessels constrict, or narrow). The RAAS consists of three major substances, including:
Renin (an enzyme).
Angiotensin II (a hormone).
Aldosterone (a hormone).
Enzymes are proteins that help trigger chemical reactions in your body. They build some substances and break others down.
Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, muscles and other tissues. These signals tell your body what to do and when to do it.
What are salivary glands?
Your salivary glands produce saliva (spit) and empty it into your mouth through or small openings. They lubricate your mouth and throat, aid in swallowing and digestion, and help shield your teeth from cavity-causing bacteria.
What are the three major salivary glands?
You have three major pairs of salivary glands, including your:
Sublingual glands: These are below either side of your tongue, under the floor of your mouth.
Submandibular glands: Located below
your jaw, your submandibular salivary glands consist of two parts: the superficial lobe and the deep lobe. Like your sublingual glands, the saliva produced in your submandibular glands enter your mouth from under your tongue.
Parotid glands: Your parotid glands are just in front of your ears. Similar to your submandibular glands, your parotid glands have two parts: superficial and deep. The saliva produced by your parotid glands enters your mouth from small ducts near your upper molars.
Function
Keeps your mouth and throat lubricated and comfortable.
Moistens food so it’s easier to swallow.
Contains an enzyme called amylase, which helps your stomach break down starches in food.
Keeps your mouth clean.
. Helps reduce your risk of cavities and gum disease.
Helps maintain, the pH balance in your mouth
Types of Nephron
There are two types of nephron: • Cortical nephron
These are the nephrons present within the cortex. These are short and comprise about 80% of the
total nephrons. • Juxtamedullary nephron
These have long loops of Henle and extend into the medulla. These are about 20%.
Functions of Nephron
The primary function of nephron is removing all waste products including the solid wastes, and other excess water from the blood, converting blood into the urine, reabsorption, secretion, and excretion of numerous substances.
As the blood passes through the glomerulus with high pressure, the small molecules are moved into the glomerular capsules and travel through a winding series of tubules.
The cell present in each tube absorbs different molecules excluding the glucose, water, and other beneficial molecules which are called as the ultrafiltrate. As the ultrafiltrate molecules travel down the tubules they become more and more hypertonic, which results in more amount of water to be extracted from the ultrafiltrate before it exits the nephrons.
The blood surrounding the nephron travels back into the body through the renal blood vessels, which are free of toxins and other excess substances. The obtained ultrafiltrate is urine, which travels down via the collecting duct to the bladder, where it will be stored and released through the urethra
