The document summarizes the key primary organs and organ systems in the human body. It discusses the five vital organs - brain, heart, kidneys, liver and lungs. For each organ, it provides details on their location, structure, functions and role in various organ systems like nervous system, cardiovascular system, renal system, digestive system and respiratory system. It also discusses the development of organs during the three trimesters of fetal growth.

1. PRIMARY ORGANS
HEMA T
MSc BIOCHEMISTRY
BHARATHIAR UNIVERSITY
2018-2020

2. Body systems
• The human body is made of 11 important organ systems.
• These systems work together to maintain a functioning human body.
Cells
Tissues
Organs
Organ Systems

3. These are the 11 organ systems
 Circulatory system
 Digestive system
 Endocrine system
 Integumentary system
 Muscular system
 Nervous system
 Reproductive system
 Respiratory system
 Skeletal system
 Urinary system
 Lymphatic system
These are the 11 Organ Systems

4. Organs
• A part of an organism which is typically self-contained and has a
specific vital function is called as an organ.
• The word organ is derived from Greek.
• It is widely believed that there are 80 organs; however, there is no
universally standard definition of what constitutes an organ.
• The number of organs varies depending on how one defines an organ.
• Newly discovered organs
• Interstitium
• Mesentery

5. Stages of Fetal DevelopmentStages of Fetal Development

6. First Trimester (1-3 Months)
These are the organs and organ systems that form during First
trimester of fetal development.
• Nervous system
• Heart
• Face
• Arms and Legs
• Sexual Organs
• Muscle and Movement

7. First Trimester

8. Second Trimester (4-6 Months)
• Development of taste buds
• Development sensory neurons
• Baby will weigh almost 2 pounds
• About 1 foot long
• All of the essential organs have formed
• Branches of the respiratory tree develop

10. Third Trimester (7-9 Months)
• In case boy, testicles descend into scrotum
• Skeleton is hardening
• Open and close eyes
• Amniotic fluid disappear
• Put on more fat
• Baby lungs fully mature now.

12. • Humans have five vital organs that are essential for survival.
• These are called as primary organs.
• They are the
• brain
• heart
• kidneys
• liver and
• lungs.
Primary Organs

13. Brain
• Brain comes under nervous system.
• Brain is situated in the skull.
• It is continued as spinal cord.
• Brain and spinal cord are surrounded by three
layers of meninges called the outer dura mater,
middle arachnoid mater and inner pia mater.
• The space between arachnoid mater and pia
mater is known as subarachnoid space.
• This space is filled with a fluid called
cerebrospinal fluid.

14. Parts of Brain

15. 1. Prosencephalon
Prosencephalon is otherwise known as forebrain. It is further divided into
two parts:
i. Telencephalon, which includes cerebral hemispheres, basal ganglia,
hippocampus and amygdaloid nucleus
ii. Diencephalon, consisting of thalamus, hypo thalamus, metathalamus and
subthalamus.
2. Mesencephalon
Mesencephalon is also known as midbrain.
3. Rhombencephalon
Rhombencephalon or hindbrain is subdivided into two portions:
i. Metencephalon, formed by pons and cerebellum
ii. Myelencephalon or medulla oblongata.
Midbrain, pons and medulla oblongata are together called the brainstem.

16. Functions of Brain

17. Do You Know?
• The human brain weighs 3 pounds.
• It comprises 60% of fat.
• It is one of the fattest organs in the human body.
• Of the total blood and oxygen that is produced in our body, the brain
gets 20% of it.
• When the blood supply to the brain stops, it is almost after 8-10
seconds that the brain starts losing the consciousness.
• The brain is capable of surviving for 5 to 6 minutes only if it doesn’t
get oxygen after which it dies.

18. Heart
• Heart comes under cardiovascular system.
• Heart is a muscular organ that pumps blood
throughout the circulatory system.
• It is situated in between two lungs in the
mediastinum.
• It is made up of four chambers, two atria
and two ventricles.

19. Heart is made up of three layers of tissues:
1. Outer pericardium
2. Middle myocardium
3. Inner endocardium
PERICARDIUM
• Pericardium is the outer covering of the heart. It is made up of two layers:
i. Outer parietal pericardium
ii. Inner visceral pericardium
Layers of Heart

20. MYOCARDIUM
• Myocardium is the middle layer of wall of the heart and it is formed
by cardiac muscle fibers or cardiac myocytes.
ENDOCARDIUM
• Endocardium is the inner most layer of heart wall.
• It is a thin, smooth and glistening membrane.
• It is formed by a single layer of endothelial cells, lining the inner
surface of the heart.

21. Valves of the Heart
• There are four valves in human heart.
• Two valves are in between atria and the ventricles called
atrioventricular valves.
• Other two are the semilunar valves, placed at the opening of blood
vessels arising from ventricles, namely systemic aorta and pulmonary
artery.
• Valves of the heart permit the flow of blood through heart in only one
direction.

22. Atrioventricular Valves
• Left atrioventricular valve is otherwise
known as mitral valve or bicuspid valve.
• Right atrioventricular valve is known as
tricuspid valve.
Semilunar Valves
• Semilunar valves are present at the openings
of systemic aorta and pulmonary artery and
are known as aortic valve and pulmonary
valve respectively.

23. Blood Vessels
Blood vessels Diamete
r
Thickness of
the wall
Elastic
tissue
Smooth
muscle fibre
Fibrous
tissue
Aorta 25mm 2mm More Less More
Artery 4mm 1mm More More Moderate
Arteriole 30μ 6μ Moderate More Moderate
Terminal
arteriole
10μ 2μ Less More Moderate
Capillary 8μ 0.5μ Absent Absent Moderate
Venule 20μ 1μ Absent Absent Less
Vein 5mm 0.5mm Less More Moderate
Vena cava 30mm 1.5mm Less More More

25. Kidney
• Kidney comes under renal system.
• Renal system includes:
1. A pair of kidneys
2. Ureters
3. Urinary bladder
4. Urethra.
• Kidneys produce the urine.
• Ureters transport the urine to urinary bladder.
• Urinary bladder stores the urine until it is voided (emptied).
• Urine is voided from bladder through urethra.

26. Different layers of kidney
Components of kidney are arranged in
three layers
1. Outer cortex
2. Inner medulla
3. Renal sinus.
1. Outer Cortex
• Cortex is dark and granular in
appearance.
• It contains renal corpuscles and
convoluted tubules.

27. 2. Inner Medulla
• Medulla contains tubular and vascular structures arranged in parallel radial lines.
• Medullary mass is divided into 8 to 18 medullary or Malpighian pyramids.
• Broad base of each pyramid is in contact with cortex and the apex projects into
minor calyx.
3. Renal Sinus
• Renal sinus consists of the following structures:
i. Upper expanded part of ureter called renal pelvis
ii. Subdivisions of pelvis: 2 or 3 major calyces and about 8 minor calyces
iii. Branches of nerves, arteries and tributaries of veins
iv. Loose connective tissues and fat.

28. Functions of Kidney
1. Role in homeostasis
2. Hemopoietic function
3. Endocrine function
4. Regulation of blood pressure
5. Regulation of blood calcium level

29. Liver
• Liver comes under digestive system.
• Liver is a dual organ having both
secretory and excretory functions.
• It is the largest gland in the body,
weighing about 1.5 kg in man.
• It is located in the upper and right
side of the abdominal cavity,
immediately beneath diaphragm.

30. Internal Structure of Liver
Hepatic Lobes
• Liver is made up of many lobes called hepatic lobes
• Each lobe consists of many lobules called hepatic lobules.
Hepatic Lobules
• Hepatic lobule is the structural and functional unit of liver.
• There are about 50,000 to 100,000 lobules in the liver.
• The lobule is a honeycomb-like structure and it is made up of liver
cells called hepatocytes.

31. Hepatocytes and Hepatic Plates
• Hepatocytes are arranged in columns, which form the hepatic plates.
• Each plate is made up of two columns of cells.
• In between the two columns of each plate lies a bile canaliculus .
• In between the neighboring plates, a blood space called sinusoid is
present.
• Sinusoid is lined by the endothelial cells.
• In between the endothelial cells some special macrophages called
Kupffer cells are present.

32. Portal Triads
• Each lobule is surrounded by many portal
triads.
• Each portal triad consists of three vessels:
1. A branch of hepatic artery
2. A branch of portal vein
3. A tributary of bile duct.
• Branches of hepatic artery and portal vein
open into the sinusoid.
• Sinusoid opens into the central vein.
• Central vein empties into hepatic vein.
• Bile is secreted by hepatic cells and emptied
into bile canaliculus.
• From canaliculus, the bile enters the tributary of
bile duct.

33. Functions of liver
1. Metabolic function
2. Storage function
3. Synthetic function
4. Secretion of bile
5. Excretory function
6. Heat production
7. Hemopoietic function
8. Hemolytic function
9. Inactivation of hormones and drugs
10. Defensive and detoxification functions

34. Lungs
• Lung comes under respiratory system.
Pleura
• Each lung is enclosed by a bilayered
serous membrane called pleura or pleural
sac.
• Pleura has two layers namely inner
visceral and outer parietal layers.
• Visceral layer is attached firmly to the surface
of the lungs.
• At hilum, it is continuous with parietal layer,
which is attached to the wall of thoracic cavity.

35. Intrapleural Space or Pleural Cavity
• Intrapleural space or pleural cavity is the narrow space in between
the two layers of pleura.
Intrapleural Fluid
• Intrapleural space contains a thin film of serous fluid called
intrapleural fluid, which is secreted by the visceral layer of the pleura.

36. Functions of intrapleural fluid
1. It functions as the lubricant to prevent friction between two layers of
pleura
2. It is involved in creating the negative pressure called intrapleural
pressure within intrapleural space.
Pleural Cavity in Abnormal Conditions
• In some pathological conditions, the pleural cavity expands with
accumulation of air (pneumothorax), water (hydrothorax), blood
(hemothorax) or pus (pyothorax).

37. Tracheobronchial Tree
Trachea and bronchi are together called tracheobronchial tree. It forms a part of air
passage.
Components of tracheobronchial tree
1. Trachea bifurcates into two main or primary
bronchi called right and left bronchi
2. Each primary bronchus enters the lungs and
divides into secondary bronchi
3. Secondary bronchi divide into tertiary bronchi.
In right lung, there are 10 tertiary bronchi and in left
lung, there are eight tertiary bronchi
4. Tertiary bronchi divide several times with
reduction in length and diameter into many
generations of bronchioles
5. When the diameter of bronchiole becomes 1 mm or
less, it is called terminal bronchiole
6. Terminal bronchiole continues or divides into respiratory bronchioles, which have a
diameter of 0.5 mm.

38. Functions of Lungs
• Changing the pH of blood (whether the blood is more acid or alkali)
by increasing or decreasing the amount of CO2 in the body.
• Filtering out small gas bubbles that may occur in the bloodstream.
• Converting a chemical in the blood called angiotensin I to angiotensin
II. These chemicals are important in the control of blood pressure.

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