Human Anatomy And Physiology 1 - Unit 1

UNIT-1

Introduction to human body

• Definition and scope of anatomy and physiology, levels of structural organization and body systems, basic life processes, homeostasis, basic anatomical terminology.
• Cellular level of organization.
• Tissue level of organization.

Important Questions

1. Define cell. Draw a well labelled diagram of cell with its organelles (parts) and write its functions.
2. Draw a well labelled diagram of plasma membrane and explain transport mechanism across plasma membrane.
3. Define Cell Division & Explain Somatic cell division with diagram (Mitosis).
4. Define Tissue and write its classification with detailed note on connective Tissue.
5. Define Homeostasis. Explain Positive and Negative feedback mechanism with example.
6. Write a short note on:
   • Mitochondria
   • Nucleus

1. Structure of Cell

Question: Define cell. Draw a well labelled diagram of cell with its organelles (parts) and write its functions.

Cell: A cell is the basic living structural and functional unit of body enclosed within a membrane.

There are about 200 different types of cells in our body. A human body consist of about $10^{14}$ or 100 trillion cells with a size and mass of about $10 \mu m$ and 1 nanogram.

Structure of the cell:

It is divided into 3 parts:

1. Plasma membrane
2. Cytoplasm (Cytosol + Organelles)
3. Nucleus

(i) Plasma membrane

Also known as cell membrane. It is the outermost membrane of cell which separate out the internal environment of cell to the external environment. It is selectively permeable which allowing substances to pass through it.

Functions:

• It provide protection from external environment.
• It regulates the flow of material into and out to the cell.
• It give shape to the cell.

(ii) Cytoplasm

It is the total area between the plasma membrane to the nucleus. It further divide into two parts:

(a) Cytosol:

• It is the fluid present inside the cells.
• It is transparent, viscous which contain about 75% to 90% water, protein, lipids & Carbohydrates.

(b) Organelles: These are the organelles present in cytoplasm and perform specific function for cell.

1. Endoplasmic Reticulum (ER): It is a complex channel system enclosed within the membrane in the form of three dimensional network that consist of vesicles, flattened sacs and branched tubules.

It is of two types:

• (i) Rough ER: Those ER which have ribosomes attached, helped in protein and membrane synthesis.
• (ii) Smooth ER: Ribosomes are not attached.

Functions:

• Act as a structural framework of cytoplasm.
• Exchange material.
• SER (Smooth ER) help in synthesis of phospholipids, cholesterol and triglycerides.

2. Ribosomes: These are tiny spheres that contain ribosomal RNA & several ribosomal proteins. Also known as factory of proteins, because protein synthesis takes place in it.
These are made up with two subunits i.e. smaller subunits (40s) and the larger subunit (60s). Total 80s.

Functions:

• Generate protein.
• Translation of genetic information encoded in nucleotide bases of DNA into amino acid sequence of proteins.

3. Mitochondria: It is also known as "Power House of cell", because it generate ATP. It is made up with two membranes i.e. inner and outer.

Function:

• Generate energy.
• Also perform cellular signalling and regulates cellular proliferation.

4. Golgi Apparatus / Body: It consist of four to six flattened sacs called as cisternae placed upon each other. Like a pile of plates with expanded bulges at their ends.

Functions:

• Stores protein, modify them and also moved to the plasma membrane through secretory granules, when required.
• Also helping in excreting excess amount of water.

5. Lysosomes: They are secretory vesicles formed from the golgi complex. They worked as the digestive system of cell, which contain digestive and hydrolytic enzymes and hydrolyse large molecules such as RNA and DNA, proteins and lipids.

Functions:

• Digests food particles carried in via endocytosis.
• Breakdowns old and damaged organelles in cell.
• Destroys harmful microorganism.

6. Centrosomes: It consists of a pair of centrioles and play an important role during cell division.

Functions:

• Produces spindle fibers during cell division.
• Play a role in intracellular transport.

7. Peroxisome: It contain many oxidases enzymes that can oxidize various organic substances such as fatty acid, amino acids, uric acid etc.

Functions:

• Participates in the synthesis of cholesterol, bile acids.
• Peroxidase enzymes detoxify alcohol from liver cells.

(iii) Nucleus

The nucleus is usually a spherical and oval shaped structure, which is largest in the cell. It contain a spherical structure called nucleolus. It also called as "Control centre.

Function:

• Stores genetic information (DNA & RNA).
• Replication of DNA.
• Site of production of ribosomes.

2. Plasma Membrane and Transport

Question: Draw a well labelled diagram of plasma membrane. Explain transport mechanism across plasma membrane.

Plasma membrane: Also known as cell membrane.

• It is the outermost membrane of cell which separate out the internal environment of cell to the external environment.
• It is selectively permeable which allowing substances to pass through it.

Structure: The fluid-mosaic model of plasma membrane was given by S.J. Singer and G.L. Nicholson.

• It is made up with bilayer of phospholipids.
• Proteins: The lipid bilayer is embedded with proteins of various shape and size.
• Carbohydrates: These molecules are attached with proteins (glycoprotein) and Lipids (glycolipid).

Functions:

• It provide protection from external environment.
• It give shape to the cell.
• It regulates the flow of material into and out to the cell.

Transport Across Membranes

Plasma membrane of cells are selectively permeable, which allow only some substance to cross it. Membrane is a biological membrane, which is made up with phospholipids bilayer and allow substance to move through it (It is known as membrane transport).

Substances are transported across the cell membrane through:

1. Passive transport
   • Passive diffusion
   • Facilitated diffusion
2. Active transport
   • Primary
   • Secondary
3. Endocytosis

Concentration Gradient: The process of transport is based on the principle of concentration Gradient. When any drug/substance move from high concentration to lower concentration. (High amount $\to$ Low amount across conc gradient)

(i) Passive transport

In this, substance transport across the conc gradient i.e. High to low.

• Passive diffusion: It is the transport of substance across the conc gradient i.e. from the region of higher conc to lower conc without use of energy. Eg. Diffusion of lipid soluble molecules like $O_2$ & $CO_2$ across the cell membrane.

• Facilitated diffusion: In this, substance transport across the conc gradient, but with the help of any Carrier bodies (it is also called as carrier mediated transport). It is suitable for poorly diffusible substance.

  • Carrier used such as SLC (solute carrier transporter).
  • Eg. Entry of glucose into RBC.
  • Intestinal absorption of Vit. $B_{12}$ & $B_2$.

• Osmosis: It is the movement of solvent (water) particle from high (solvent) to low conc through semipermeable membrane (from low solute conc to high solute conc).

(ii) Active transport

In this, substance transport against the conc gradient with the help of energy. In this, ATP is used. $ATP \xrightarrow{hydrolysis} ADP$

It is of two types:

• Primary active transport: In this, ATP is used as energy. Eg. Absorption of glucose. (Low conc $\to$ High conc).
• Secondary active transport: In this, electrochemical gradient are used instead of energy.
  • Symport (Co-transport): Movement of both substance in same direction. Eg. $Na^+$-glucose symport.
  • Antiport (Counter-transport): Movement of molecule in opposite direction. Eg. $H^+ - Na^+$ pump.

(iii) Endocytosis

In this transport, drugs of very large size molecules get transported via engulfment by cell membrane.

• Cellular uptake of macromolecular like fat, oil, Starch, Soluble vitamins like A, D, E, K and drug like insulin.

• Phagocytosis [cell eating]: Absorptive uptake of solid particulates.
• Pinocytosis [cell drinking]: Uptake of fluid solute.

3. Cell Division

Question: Define Cell Division & Explain Somatic cell division with diagram.

It is a process by which a parent cell divides into two daughter cells. The genetic content (DNA) of newly formed cell is exactly same to the parent cell.

Cell division is of two types:

1. Mitosis: Responsible for growth of cells. Number of chromosomes same [equational division]. Occurs in somatic cells.
2. Meiosis: Responsible for formation of gametes cells. Occurs in reproductive cells and no. of chromosomes decreased [Reductional division].

Mitosis

Also known as M-phase or Mitotic phase [Equational division]. It occurs in somatic cell in which already existing parent cell divides into two identical daughter cells. In this, the no. of chromosome in daughter cell is same as the no. of chromosome in parent cell.

It is occurs into two parts:

1. Karyokinesis (P-M-A-T)
2. Cytokinesis

(i) Karyokinesis

It is a process by which the cell nucleus divides into two daughter nuclei.

• Prophase: This phase begins with initiation of condensation of the chromosomal material i.e. Chromatin. Centrioles [centrosome] moves towards the opposite poles of the cell. Organelles like golgi complex, ER, Nucleolus and Nuclear envelope disappear at the end of prophase.
• Metaphase: This phase begins with complete disintegration of nuclear envelope. Chromosomal condensation completed and two sister chromatids holds together by centromere. Kinetochores (small disc shaped) are at the surface of centromere. Spindle fiber attach to kinetochores and chromosome moved to spindle equator and get aligned.
• Anaphase: Begins with splitting of each chromosomes. Separation of chromatids and move towards opposite poles.
• Telophase: Last stage of mitosis and in this chromosomes loose individuality (decondensation) and chromatin material is collected as a mass at two poles. Nuclear membrane reappear and two nuclear formed. Other organelles reappears.

(ii) Cytokinesis

It is the division of cytoplasm after nucleus division to form two daughter cells.

Cell Cycle

The sequence of events by which a cell duplicate its genome, Synthesis the other constituents (organelles) of the cell and eventually divides into two daughter cells.

It has two phases:

1. Interphase (Resting phase / Preparation phase)
   • $G_1$ Phase
   • S Phase
   • $G_2$ Phase
2. M-phase (Mitotic Phase / Cell division)

• $G_1$ Phase (10 hrs): First growth phase. ATP, Nucleotides, RNA & Protein synthesis. Preparation for DNA replication.
• S Phase (9 hrs): Synthesis phase. DNA replication. Replication of chromosome. Centriole duplication.
• $G_2$ Phase (4 hrs): Second growth phase. Preparation for mitosis. RNA & Protein synthesis.
• M-Phase (1 hr): Cell-division. (Prophase, Metaphase, Anaphase, Telophase, Cytokinesis).
• $G_0$ Phase: Cells that do not divide further exit $G_1$ phase to enter an inactive stage called quiescent stage ($G_0$) of the cell cycle.

4. Tissues

Question: Define Tissue and write its classification with detailed note on connective Tissue.

Tissue: It is a group of some cells which have similar structure and functions. Each tissue carries out a unique functions in body. They are only found in multicellular organism. Histology: It is the branch of science that deals with the study of tissue.

(Cells $\to$ Tissue)

Classification of Tissue

Tissues are classified into four major types based on their structure and functions.

1. Epithelial tissue
2. Connective tissue
3. Muscular tissue
4. Nervous tissue

Connective Tissue

These are those tissue which connects or bind different organs or different parts of an organs. It is the most diverse and widespread tissue in the human body, found in almost every organ of the body. Connective tissue is composed of large amount of extracellular matrix (ECM), limited number of cells, fluids and number of fibres.

Types of Connective Tissue:

1. Loose C.T.
   • Areolar C.T.
   • Adipose C.T.
   • Reticular C.T.
2. Dense Connective T.
   • Dense regular
   • Dense irregular
   • Elastic
3. Others
   • Cartilage
   • Bone
   • Blood

1. Loose connective tissue

These are those in which cells and fibres are loosely arranged with ground substances in Matrix. It is well vascularized and provides blood supply to nearby epithelial tissue. It is most widely distributed tissue which connects several body structure by acting as elastic glue which allow movement.

• Areolar Connective Tissue: Strength, Connectivity.

  • It connects the skin to the underlying structures. It works same as loose connective.
  • It is located between muscles, below the skin, blood vessels & nerves.

• Adipose Connective Tissue:

  • It contain adipocytes (fat cells), which store energy (glucose) for the body.
  • It is located under the skin b/w internal organs, bone marrow.
  • It store energy in the form of fat. Brown fat produce heat generation.

• Reticular Tissue:

  • The Reticular network is formed by thin, branches of reticular fibres.
  • It is located in spleen, lymph nodes and bone marrow.
  • It provide protection and helps in the production of blood cells.

2. Dense Connective tissue / Dense fibrous

These are those tissue which are densely packed and form rope like structure. They mainly contain fibrocytes, fewer fibroblast cells and fibres in large amounts.

• Dense irregular Tissue:

  • In this, Collagen fibres are arranged in irregularly (random).
  • It is arranged in the form of thick mat like strong connective tissue.
  • Covering of organs such as kidney, spleen etc.

• Dense regular tissue:

  • In this, collagen fibres are arranged in parallel, regular. They provide strong attachment, flexibility.
  • It is present in tendons (attach muscles to bone).

• Elastic Dense tissue:

  • In this, elastic fibres are arranged parallel to each other. It provides elasticity with strength.
  • Trachea, lungs, Bronchi etc.

3. Specialized Connective Tissue

• Cartilage: It is strong, flexible connective tissue. It contain only one type of cells i.e. chondrocyte which produces the fibres and the tough, rubbery ground substance of cartilage. It protects joints and bones. It is present at the end of bones and helps in the formation of bones.
• Bone (Osseous tissue): It is the hard connective tissue, that contain a high concentration of salts like calcium phosphate and calcium carbonate (minerals). It is located in Arms, legs, Ribs etc. It also consists of collagen fibres and it provides protection and structural framework.
• Blood: It is liquid connective tissue which are formed in bone marrow and other tissue. It is composed of 55% plasma and 45% cells. The Blood cells are - RBC (Red blood cells), WBCs (white blood cells), Platelets. It helps in connects different tissue and transportation of gases, nutrients, drugs etc. Body defence System.

Functions of Connective tissue:

• It connects different tissue of body.
• It work as structural framework of body.
• It supports various tissue, organs and structures of the body.
• Blood helps in transportation of $O_2$ and nutrients and also provide defence system for body.
• It helps in formation of clots to stop bleeding.
• It helps in removal of waste product such as carbon dioxide and Urea.

5. Homeostasis

Question: Define Homeostasis. Explain Positive and Negative feedback mechanism with.

Homeostasis: It is derived from two greek word: Homeo (Same/Constant) + Stasis (State). It is a condition when our internal environment is constant with respect to external environment. Homeostasis is the body's self-regulating mechanism that keeps its internal conditions constant, even when external environment changes.

Homeostasis Control Mechanism: All the body organ coordinate with each other to maintain homeostasis. This coordination is mainly controlled by Neuroendocrine System [Nervous + Endocrine system]. It has three components:

1. Receptors: It is a type of sensor, which receive/detect changes or other stimuli.
2. Control Centre: It receive the stimuli from receptors and analyse it.
3. Effectors / feedback system: If there are any change take place in internal environment, then feedback system is take back into its constant state or in homeostasis.

It is of two types:

1. Positive feedback System
2. Negative feedback System

1. Positive feedback System: (Used to increase) When anything is decrease in our internal environment then it is try to back into its normal situation by increasing it.

• Example: During childbirth, it stimulate the release of oxytocin which increases the contraction of the uterus to help in childbirth.

2. Negative feedback System: (Used to decrease) When anything is increase in our internal environment (body), then this system is try to back into normal condition by decreasing it.

• Example: Fever (Temp).
  • Skin heat ($\uparrow$) $\to$ Signal $\to$ Hypothalamus (Temperature Regulation Centre - TRC)
  • Stimulates $\to$ Cooling body
  • Sweating ($\uparrow$) by Sweat gland
  • Temperature (\downarrow$) $\to Homeostasis

6. Short Notes

(i) Mitochondria

It is known as the Power House of cell because they generate most of the energy ATP that the cell needs to function.

It is made up with two membranes i.e. inner and outer. The main function is to generate energy. Also perform cellular signalling and regulates cellular proliferation.

It have two main parts:

1. Inner Membrane: It contain enzymes and proteins involved in energy production. It is mainly a phospholipid bilayer that folds into series of cristae, increasing the surface area for energy production.
2. Outer membrane: A phospholipid bilayer that surrounds the mitochondrion.

Functions:

• Mitochondria convert glucose into ATP.
• Mitochondria are the site of the citric acid cycle, which produces ATP, NADH and $FADH_2$.
• It maintain cellular homeostasis.
• It store calcium and other ions, regulating their release and uptake.
• It is specialized for high-energy production in muscle cells and detoxification & metabolism in liver cells.

(ii) Nucleus

The nucleus is usually a spherical and oval shaped structure, which is largest in the cell. It consist of double membrane which separate nucleus from the Cytoplasm. It contain a spherical structure called nucleolus. It is also known as "Control centre" of the cell. It contain the genetic material including aggregations of protein DNA & RNA. It directly involves in the reproduction and transfer all genetic information from parent cell to daughter cells.

Functions:

• It contain most of the cell's genetic material.
• It controls the cell growth.
• It regulates gene expression by transcribing DNA into RNA.
• It maintain genome stability by repairing DNA damage and regulating telomere length.
• It receives and responds to signals from the cytoplasm, regulate various cellular processes.