short notes

 

 A. FORMATION OF THE PLACENTA :-

 • the placenta is the organ that carries out respiration, excretion and nutrition of the embryo , and is fully formed during the 4th month.

 • the placenta develops as the embryo invades the endometrium of the uterus called implantation.

 • after implantation , the endometrium is called decidua.

 • the placenta is fromed partly from embryonic structures and partly by decidua.

 • embryonic structures trophoblast forms the villous chorion. The formation of the villous chorion proceeds through three stages: primary chorionic villi, secondary chorionic villi, and tertiary chorionic villi.

 • By the 4th month of pregnancy , the placenta is well developed organ. Fully formed placenta is about 6 inch in diameter, 500 gm in weight.

 • It has two surface maternal surface and fetal surface.

 B. FORMATION OF UMBILICAL CORD

 • There is a opening called primitive umbilical ring on the ventral surface of the developing embryo. Through which three structures pass : Vitelline duct(yolk sac), connecting stalk and allantois.

 • When amnion expands , it squeezes these three duct and together forms primitive umbilical cord.

 • At week 6, the gut tube connected to the yolk sac herniates (called the physiological umbilical herniation) into the extraembryonic coelom. By week 11 ,the gut tube returns to the abdominal cavity. The yolk sac (vitelline duct) and allantois degenerate.

 • The definitive umbilical cord is pearl-white, 1–2 cm in diameter, 50–60 cm long, eccentrically positioned, and contains the right and left umbilical arteries, left umbilical vein, and mucus connective tissue (Wharton jelly).

 C. FORMATION OF GERM LAYER:-

The embryo proper acquires the froms of three-layered disc, called embryoinc disc.

The three layered are:-

 1. Endoderm (inside) : Some cell of the inner mass cells that line free surface become flatened. Thus it is the first germ layer to be formed.

 2. Ectoderm(Outside):- The remaining cells of the inner cells mass become columnar . Thus it is second germ layered to be formed.

 3. Mesoderm(in the middle): The cells multiplying in the primitive streak moves in gap between ectoderm and endoderm , and forms mesoderm-the third germ layer.

 D. CELL DIVISION:-

Cell division is the process by which a parent cell divides into two or more daughter cells.

There are two types of cell division: -

Mitosis:-

a process of cell divison in which a single cell divides into two identical daughter cell.

Mitosis is further divided as :

 1. Interphase: - The period between two successive divisions is called the interphase.

 2. Prophase

 • chromosome becomes gradually more and more coiled like thread.

 3. Metaphase

 4. Anaphase

 5. Telophase

Meiosis:-

 • Meiosis is a specialized process of cell division that occurs only during the production of gametes within the female ovary or male testes

 • Meiosis consists of two divisions (meiosis I and II),which result in the formation of four gametes,

 • Events that occur during meiosis I are Synapsis , Crossing over ,Alignment ,Disjunction and Cell division( formation of two secondary gametocytes)

 • in meiosis II - Synapsis and Crossing over are absent. Cell division- results in formation of four gametes(23 single chromosomes, 1N)

 E. Achilles tendon:-

 • The tendo calcaneus( also known as Achilles tendon) is the thickest and strongest tendon of the body.

 • It is about 15 cm long.

 • It begins near the middle of the leg, and is attached to posterior surface of calcaneum

 • its anterior surface receives fleshy fibres of the soleus almost up to its lower end.

 • It is narrow and thick in the middle, and expanded at both end .

 • Tenda-Achilles reflex or ankle jerk :- The foot gets plantar-flexed on tapping the tendo calcaneus .

 F. RDIAL ARTERY:-

Radia artery is the smaller terminal branch of the brachial artery in the cubital fossa.

As compared to the ulnar artery, it is superficial.

Relations:-

 1. Anteriorly:- in upper part, It is overlapped by the brachioradialis.

 in lower half, it is covered only by skin, superficial and deep fasciae.

 2. Posteriorly:- It is related to the muscles attached to anterior surface of radius. i.e. biceps brachii, pronator quadratus etc.

 3. Medially:- in upper one-third, it is related to the pronator teres. in

 lower two-thirds, it is related to tendon of the flexor carpi radialis.

 4. Lateraly:- Brachioradialis and radial nerve.

Branches:-

it gives following branches in forearm:

 1. radial recurrent artery-it arises just below the elbow

 2. Muscular branches

 3. palmar carpal branch

 4. Dorsal carpal branch

 5. superficial palmar branch - arises just before the radial artery leaves the forearm.

 G. FEMORAL VEIN:-

 • at the lower end of the adductor canal, It begins as an upward continuation of the popliteal vein.

 • behind the inguinal ligament, it ends by becoming continuous with the external iliac vein.

 • Tributaries:- It receives:

 a. great saphenous vein

 b. veins that accompany three branches of femoral artery in femoral triangle i.e.profunda, deep external pudendal, and muscular.

 c. Lateral and medial circumflex femoral veins

 d. descending genicular and muscular veins in the adductor canal

 H. CORONARY ARTERY

 • The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle.

 • The coronary arteries wrap around the entire heart.

 • it Arise from the ascending aorta.

 • there are two coronary artery - Right Coronary Artery and Left Coronary Artery.