I neeD moRe Medicine

The Female Reproductive System

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The Female Reproductive System

(Fig. 32)

-The internal female genital organs are the 2 ovaries, the 2 uterine tubes, the uteruSand the vagina

Ovaries:

The ovaries are 2 almond-shaped bodies (I x 2 x 3 cm), one on either side, close, to the lateral wall of the pelvic cavity suspended to the posterior wall of the broad lisament.

The ovaries produce the ova and the female sex hormones.

Uterine (Fallopian) tubes:

There is one uterine tube on each side between the ovary and the uterus. It carriers the ova from the ovar> to the uterus.

Each tube consists of 4 parts:

1. The lateral part is funnel-shaped and is called the infundibnium. It has linger-like processes called the fimbriae. One of these fimbria has an ostium to pike up the ovum.

2. The next part is dilated and it is called the ampulla. It is

the part where fertilisation occurs.

3. The medial part is narrow and it called the isthmus.

4. The uterine end which pierces the uterus is called the intramural part.

Uterus:

- The uterus is a pear-shaped hollow organ with a thick muscle wall 1x2x3 inches.

- It lies in the pelvis behind the urinaiy bladder, in front of the rectum and above the vagina.

- It consists of 3 parts:

1. The fundus; which is the par! above the level of the uterine tubes.

2. The body, which is the main part that has a triangular cavirs where the embryo is kept until il is bom.

3. The cervix: which is the Sower part. Its lumen is fusiform and it opens above into the body by the internal os and below into the vagina by the external os.

Vagina:

- It is the tube which leads to the body surface at the vestibule of the vulva. It is directed downwards and forwards between the urinary bladder and urethra anteriorlv and the rectum posteriorly.

- Its upper part surrounds the lower part of the cervix.

- Its posterior wall is longer (9.5 cm) than its anterior wall (7.5 cm).

The external female genital organs:

Are the mons pubis, labia majora, labia minora, clitoris, vestibule of vagina. The vaginal orifice is covered in the vergin by a perforated membrane called the hymen.

The Male Reproductive System

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The Male Reproductive System

(Fig. 30)

The male genital organs are the 2 testes, the 2 epididymes, the 2 vas deference, the 2 seminal vesicles, the postate gland and the penis.

Testis: (Fig. 31)

ll is the primary male sex organ. It is oval in shape and it is about 2 inches x one inch. It lies one on each side of the scrotum in whieh it is suspended by the spermatic cord. The testis is divided into compartments containing the seminipherous tubules where spermatozoa are formed. The testis also produces the male sex hormone testosterone.

Epididymis: (Fig. 31)

It is a crescent-shaped structure that lies on xhi posterolateral aspect of the testis. It is composed of a tortuous tube which is shaped to form a head, a body and i tail. It transmits the seminal fluid from the testis to the deference.

Vas deferens, seniles! vesicle and ejaculatory duct:

The vas deferens is a long cord-like tube with narrow lumen that begins It runs as a continuation of the tail of the epididymis with the spermatic cord through the inguina canal to reach the back of the urinary bladder where it join: the duct of the seminal vesicle to form the ejaculatory due which traverses the prostate gland to open in the prostatic urethra.

Prostate gland:

It is a firm conical structure that lies below the neck of the urinan bladder surrounding the upper pan of the urethra. It is tra\ ersed b\ the ejaculaton. ducts It adds its secretion to the seminal fluid.

Penis:

- It is the copulator> organ of male b\ which spermatozoa are introduced into the female reproductive tract.

- It is formed of three erectile bodies. 2 dorsal corpora caveronsa and one ventral corpus spongiosum The latter expands at both ends and contains the urethra till external urethral meatus.

The urinary system

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The urinary system

(Fig. 29)

The urinary system consists of the kidneys, ureters, urinary bladder, and urethra

kidneys:

- The kidneys remove from the blood the toxic waste products of protein metabolism (urea and uric acid), water and inorganic salts.

- The kidneys are reddish brown, bean-shaped organs, located on the posterior abdominal wall, one on each side of vertebral column behind the peritoneum opposite the last thoracic and the upper 2 or 3 lumber vertebrae. The left kidnev is sliahtlv higher. Each kidnev is about 4 inches long. 2 inches wide, and 1 inch thick.

- The kidneys are held in place by a capsule of fat.

- Each kidney has 2 surfaces (anterior and posterior). 2 borders (medial and lateral), and 2 poles (upper and lower).

- The anterior surface is related to different structures on both sides. The right kidney is related to the liver, duodenum, right colic flexure, and coils of small intestine. That of the left kidnev is related to the pancreas, spleen, stomach. Jejunum, and descending colon.

- The posterior surface is related on both sides lies to the muscles of the posterior abdominal wall.

- The lateral border is convex.

- The medial border is concave in the middle part where it presents a slit called the hilum that gives passage to the renal vessels anteriorly and the pelvis of the ureter posteriorly. The hilum lies at level of first lumbar vertebra.

- The upper pole on both sides is related to the corresponding suprarenal gland.

- The lower pole on each side is slightly above the iliac crest

- Each kidney contains more than one million unites called nephrons.

Ureters:

The ureter is a tube which actively propels the urine towards the urinary bladder by peristaltic contractions.

It is 10 inches long. Its upper end is dilated and divided into a number of calyces, (minor calyces receive the collecting ducts and join to form major calyces). The abdominal part passes behind peritoneum on the psoas major muscle. The pelvic part enters the pelvis and turns medially to enter the back of the urinary bladder.

Urinary bladder:

The urinary bladder is a hollow muscular organ, located in the pelvic cavity behind the pubic bone. Its function is to store and to expel urine.

When fixed, it is a tri-sided pyramid with an apex anteriorly and a base posteriorly. The ureters pierce the

upper part of the base obliquely to prevent back flow of urine. The neck of the bladder is the lowest part and is continuous downwards with the urethra. The neck is surrounded by an involuntary smooth muscle sphincter, controlled b> autonomic nerves. The triangular area between the urethra and ureteric orifices is called the trigone.

Urethra

It is the tube which extends from neck of the urinary bladder to the body surface at the external urethral orifice.

Male urethra: (Fig. 29)

It is about 20 cm long. It is divisible into 3 parts:

1. The prostatic urethra: is about 3 cm long and it is surrounded by the prostate gland. It receives the 2 ejaculatory ducts.

2. The membranous urethra: is the shortest part. It is 2 cm long and it is surrounded by striated muscle.

3. The penile urethra (or spongy urethra). It is about 15cm long. It traverses the corpus spongiosum of the penis till it opens at the external urethral orifice which is the narrowest point.

Female urethra: li is about 4 cm long and it lies anterior to the vagina.

THE DIGESTIVE SYSTEM 3

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2-1

THE DIGESTIVE SYSTEM 3

The descending colon:

It is about 25 cm in length. It extends from the splenic flexure to end at the inlet of the pelvis where it joins the pelvic colon.

The pelvic colon

It is about 40 cm in length. It begins at the inlet of the pelvis and ends at the middle of the sacrum where it is connected with the rectum.

It forms a loop and it is surrounded by a peritoneal fold called pelvic mesocolon, so it is freely movable and hangs in the pelvic cavity.

The rectum:

It is about 12 cm in length. It begins at the middle of the sacrum and ends below the coccyx where it opens into the anal canal. In human, it is not straight as its name implies but it rather forms 3 flexures two convex to the right and one to the left.

The anal canal:

It is about 4 cm in length and ends below, in the perineum by the anal opening (anus). Interna) and externa! sphincters control the opening.

The peritoneum:.

It is a serous membrane formed of two layers; i parietal layer lining the wall of the abdomen, and a viscera Saver covering the abdominal viscera. ~

In some regions it extends as a fold formed of ‘. layers to connect the internal organs with the abdomina

wall, e.g. the mesentery and the transverse mesocolon, so that it facilitates the movement of organs of alimentary canal.

The glands associated with the alimentary canal:

1. The Salivary glands: (Fig. 27)

There are three pairs of salivary glands, which secrete the saliva into the mouth.

1. The parotid glands: located one on each side in front and below the external ear. Each gland has a duct that opens in the vestibule of the mouth opposite the upper 2nd molar tooth.

2. The submandibular glands: located below the body of the mandible near its angle. Their ducts open under the tongue on the sublingual papillae.

3. The sublingual glands: located directly under the
tongue, covered by the mucous membrane of the floor of
the mouth, raising the two sublingual folds. They open by
numerous short ducts (8-20) in the floor of the mouth.

II. The pancreas:

The pancreas extends transversely on the posterior abdominal wall in front of the upper two lumbar vertebrae. It is 15 cm in length. Its expanded right part is called the head and it is surrounded by the duodenum. The head is followed by a constricted part called the neck, which lies in front of. the portal vein. The neck is followed by the main part called the body. .The left tapering end of the pancreas is the called the tail which rests on the spleen. The pancreas serves both exocrine and endocrine functions. It secretes the

pancreatic juice and the hormone, insulin. The duct of the pancreas, which transmits the pancreatic juice, opens with the common bile duct in the middle of the second pan of the duodenum.

III. The liver:

The. liver is a large gland weighing over 1.5 kg. It is wedge shaped with its base directed to the right and its apex directed to the left.

It lies principally in the right hypochondrium but stretches across the epigastrium to reach the left hypochondrium.

It is divided into two man lobes; a large right lobe and smaller left lobe. A smaller part; the quadrate lobe, is demarcated on the inferior surface of the right lobe and another circumscribed part on its posterior surface is called the caudate lobe.

The porta hepatis is an opening on its inferior surface behind the quadrate lobe through which the right and left hepatic ducts, the hepatic artery and the portal vein pass in that order from before backwards.

Blood supply of the liver:

The liver has a dual blood supply:

a) Oxygenated blood form the hepatic arterv which arises form the coaliac trunk: a branch from the aorta.

b) Portal venous blood from the portal vein.

The blood leaves the through the hepatic veins to the inferior vana cava. The liver is the site of very many vital metabolic processes. It also secretes bile.

The biliary apparatus:(Fig. 28)

It consists of the ducts through which the bile is transported and the gall bladder, which concentrates it.

Interlobular ducts discharge their contents into the tributaries of the right and left hepatic ducts, which leave

the liver through the porta hepatis and unite to form the common hepatic duct (3cm in length).

The common hepatic duct unites with the cystic duct from the gall bladder to form the common bile duct (7.5 cm in length).

The common bile duct opens together with the

pancreatic duct in the middle of the second part of the duodenum.

The gall bladder is a pear shaped organ 7 -10 cm in length having a capacity of about 30-50″ ml. it is attached to the inferior surface of the liver to the right side of the quadrate lobe.

It consists of a fundus; which project beyond the inferior margin of the liver, a body and the neck which is the narrow part following the body and continuous with the evstic duct. The cystic duct is 3-4 cm in length. It unites with the common hepatic duct at an acute angle to form the common bile duct.

THE DIGESTIVE SYSTEM 2

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THE DIGESTIVE SYSTEM 2

The stomach: (Fig. 26)

It is the most distensible part of the alimentary tract It transmits food from the oesophagus to the duodenum, li lies in the upper left part of the abdominal ca\iiy below the diaphragm.

It has two openings: the cardiac orifice lying ai the junction with the oesophagus and the pyloric orifice a! the junction of the stomach with the duodenum.

It has two surfaces; anterior and posterior, and r»< borders called the lesser and the greater curvatures. The

lesser curvature is the concave right border while the greater curvature is the larger (4 times larger) convex left border. The stomach is divided into two portions:

a) Cardiac portion: It includes, the cardiac orifice, the fundus (which is the part above the cardiac orifice) and the body (which follows the fundus and it is the largest part of the stomach).

b) Pyloric portion: It includes the pyloric antrum that follow the body of the stomach, the pyloric canal which is the cylindrical part the follows the pyloric antrum and the pylorus which is the part corresponding to pyloric orifice, it contains the thick pyloric sphincter.

The position and shape of the stomach vary in different people and in the same individual depending on its content and the person’s position.

The stomach is capable of holding up to 3 liters of material in the adult. In the newborn, the stomach is about the size of the hen’s egg, and it can hold about 30 ml of fluid. The stomach functions as a reservoir for food and it secretes the digestive juice which contains hydrochloric acid and certain enzymes.

The small intestine:

The small intestine extends from the pylorus of the stomach to the ileocaecal junction where it joins the large intestine. It is about 6 meters (20 feet) long and it is divided into three parts; the duodenum, the jejunum, and the ileum. The jejunum and ileum are connected to the posterior abdominal wall by a peritoneal fold called the mesentery.

a) The duodenum:

It is 25 cm (10 inches) long. It lies on the posterior abdominal wall behind the peritoneum. It is C-shaped and it surrounds the head of the pancreas.

The bile duct and the pancreatic duct unite and open by a common opening in the posteromedial part about the middle of the duodenum. For descriptive purposes, the duodenum consists of 4 parts: 1* part above the head of the pancreas, 2nd part on its right side, 3^rd part below it, and 41h part on its left side.

b) The jejunum:

It is called so because it contains no food after death. It comprises the upper 2/5 of the small intestine distal to the duodenum.

c) The ileum:

It is called so because it is the most coiled part of the small intestine. It comprises the following 3/5 of the small intestine.

Differences between the jejunum and ileum:

1 No.	Jejunum	Ileum
1 ⁵	Larger in diameter	Smaller in diameter
2.	The mesentrv contains small amount of fat so the blood vessels can be seen	The mesentry contains much fat obscuring its blood vessels
3.	The circular folds of the mucosa and the villi are larger and more numerous	The circular folds and villi of the mucosa are smaller and less numerous

Function of the small intestine:

The upper part of small intestine is mainly digestive, while its lower part is mainly absorptive.

The large-Intestine:

The large intestine extends from the ileocaecal junction to the anus; it is about 1.5 m long. It consists of the caecum and vermiform appendix, the ascending colon, the right colic flexure (hepatic flexure), the transverse colon, the left colic flexure (splenic flexure), the pelvic colon, the rectum and anal canal.

Differences between the large and small intestines:

No.	Large intestine	Small intestine
1	It has a greater calibre.	It has a lesser calibre
2.	It is 1.5 m in length	It is 6m in length
3. The external surface i j contains sacs full of fat i called ! appendices epiplociae.		The external surface does not contain appendices epiplociae.
4.	The longitudinal muscle ; layer forms 3 longitudinal \| bands called taeniae col! ! which are shorter in length ! than the true length of the S large intestine so that the ! wall presents ilia titrations ! (sacculations).	The longitudinal muscle layer does not form bands 2nd the wall of the small intestine is smooth without haustrations.

The caecum

The caecum is present in the right iliac fossa. It is 6cm long. It is a blind pouch which- is continuous above with the ascending colon.

The ileum opens into the large intesine at the junction between the caecum and ascending colon. The vermiform appendix opens into the posteromedial aspect of the caecum about one inch (2.5cm) below the ileocaecal junction.

The vermiform appendix:

A very narrow worm-like tube which opens into the posteromedial aspect of the caecum about one inch (2.5 cm) below the ieocaecal junction.

Its average length is 9cm. It usually lies behind the caecum (retrocaecal) or extending into the pelvis (pelvic).

The ascending: colon: It is about 15 cm in length.

It begins at the upper end of the caecum and extends to the inferior surface of the liver, where it bends to the left to

form the right flexure (hepatic flexure) which connects it with the transverse colon.

The transverse colon:

It is about 50 cm in length. It extends transversely across the abdomen from the hepatic flexure to the left splenic flexure where it continues as the descending colon. A peritoneal fold called the transverse mesocolon surrounds it, so it is freely movable.

THE DIGESTIVE SYSTEM 1

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THE DIGESTIVE SYSTEM 1

(Fig. 23)

The digestive system consists of the mouth, the pharynx, the oesophagus, the stomach, the small intestine and the large intestine. It also includes the associated glands as the salivan glands, the liver, and the pancreas.

The mouth:

- The mouth is the first part of the digestive tube and it is also used in breathing. The mouth is composed of a smaller outer part called the vestibule and a larger inner part called the mouth cavity proper.

- The vestibule is bounded externally by the cheeks and lips and internally by the teeth and gums.

- The operture between the lips is called the oral fissure.

- The mouth cavity proper is bounded anteriorly and on each side by the teeth and gums. Posteriorly it communicates with the oropharynx. The roof is formed b> the hard and soft palates which separate it from the nasal cavity The floor of the mouth is principally formed b> the tongue and the sublingual salivary glands, which raise a ridge of mucous membrane called the sublingual fold.

The LIPS:

The lips are the two muscular folds surrounding the oral fissure. /They are covered externally by the skin and internally by mucous membrane. Between the outer skin and inner mucosa is the vermilion which is the red zone to which lipstick is sometimes applied. It appears red because of the presence of capillary loops close to the surface.

The GUMS

The gums are composed of fibrous tissue, which is covered by mucous membrane. They are attached to the margins of the alveolar processes of the upper and lower jaws and to the neck of the teeth.

The Tongue:

The tongue is a highly mobile muscular organ concerned with chewing, taste, swallowing, articulation (speech), and oral cleaning. It has an .upper surface, a lower surface, and two lateral borders.

The teeth:

The teeth are set in sockets in the alveolar processes of the jaws. There are two sets of teeth: deciduous (or milk) teeth, and permanent teeth.

Milk teeth are ten in each jaw i.e. 5 in each half of a jaw: 1 central incisor, 1 lateral incisor, 1 canine, and 2 molar teeth. They erupt during the first 2 years of life starting usually at the sixth month. They are usually shed from the sixth to the twelfth year as they are replaced by the permanent teeth.

Permanent teeth (Fig. 24) replace the milk teeth between the 6^th and 18^th year. Each adult jaw contains 16 permanent teeth i.e. each half of a jaw contains 8 teeth: 1 central incisor, 1 lateral incisor, 1 canine, 2 premolars and 3 molars.

N.B. incisors are the cutters. Canines are piercers. Premolars and molars are the grinders.

Each tooth (Fig. 25) has a crown above the gingivae a neck embedded in the gingivae, and a root fixed in the socker of the alveolar process of the jaw by a fibrous periodontal membrane. Most of the tooth is composed of dentine which is covered b\ enamel over the crown and cementum over the root. The pulp cavity contains connective tissue, blood vessels and nerves and is continuous with the periodontal tissue through the root canal.

The pharynx:

See the respiratory system.

The oesophagus:

The oesophagus is a muscular tube about 25 cm in length. It extends from the lower end of the pharynx to the cardiac orifice of the stomach. It passes in the neck (cervical part), in the thorax (thoracic part), and in the abdomen (abdominal part). It transmits the food from the pharynx to the stomach.

The cardiovascular system 2

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1 The cardiovascular system 2

The most important arteries are:

1, The aorta (Fig. 21): It is the largest artery in the body. It carries the pure oxygenated blood from the left ventricle to all parts of the body.

It is described as consisting of 3 parts:

a)Ascending aorta: from its origin from the left ventricle, it

ascends upwards, forwards and to the right.

b) Arch of aorta: it arches backwards and to the left to reach the vertebral column at the lower border of the fourth thoracic vertebra.

c) Descending aorta: which descends in the thorax behind the pericardium and diaphragm to pass from the thorax to the abdomen.

2. The pulmonary trunk: carries the deoxygenated blood from the right ventricle to the lungs. It divides under the arch of the aorta into right and left pulmonary arteries which pass to the right and left lungs respectively.

3. The coronary arteries: these are the right and left coronary arteries. They arise from the ascending aorta just after its commencement. In general, each artery supplies the atrium and ventricle of its corresponding side.

The most important veins are:

1. The superior Vena Cava: it carries the impure deoxygenated blood from the upper limbs, the head and neck, and the brain to the right atrium.

2. The inferior Vena Cava: it carries the impure

deoxygenated blood from the lover limbs, pelvis, and trunk to right atrium.

3. The four pulmonary Veins: They are two form each lung. They carry the oxygenated blood from the lungs to the left atrium.

4. The portal vein (Fig. 22): The porta! %ein carries the blood from the alimentary canal and the spleen to the liver. It is formed by the union of the superior mesenteric vein and the splenic vein behind the neck of -37pancreas then it runs superiorly to reach the liver where it divides into two branches, right and left. Each branch -enters the corresponding lobe of the liver. The most important of its tributaries beside the two veins forming it are the inferior mesenteric vein and the gastric veins.

The blood circulation:

In the human body, the circulation of blood consists of 3 parts; the systemic circulation, the pulmonary circulation and the portal circulation.

a) The pulmonary circulation:

Through the pulmonary circulation the blood is purified (oxygenated) in the lungs.

When the right ventricle contracts, the blood is pumped to both lungs through the pulmonary trunk and pulmonary arteries.

In the lungs, purification of blood through gas exchange occurs.

The blood then returns from the lugs to the left atrium by the 4 pulmonary veins.

b) The systemic circulation:

Trough the systemic circulation, all parts of the body are supplied with pure oxygenated blood and nutrients.

When the left velltricle contracts the blood is pumped to all parts of the body through the aorta.

In the tissues of the body, exchange of gas and nutrients takes place.

The impure deoxygenated blood returns from the body tissues to the right atrium along the superior and inferior venae cavae.

c) The portal circulation (Fig. 22):

Through the portal circulation, the nutrient materials absorbed in the intestine are metabolized in the liver.

This circulation includes the outflow of pure blood from the left ventricle through the aorta to reach the stomach, intestine, pancreas and spleen.

Then the impure blood loaded with nutrients is collected from these viscera by the tributaries of the portal vein to enter the liver along its two branches.

Then the blood flows out from the liver through the two hepatic veins (right and left) to the inferior vena cava and from there to the right atrium.

The places where you can feel the pulse:

- The lower part of the radial artery.

- The brachial artery in front of the cubital fossa.

- The dorsalis pedis artery in the foot (in the interval between the metatarsals of the first and second toes.

- At the apex beat (in the interval between left 5^th and 6^thribs just below and medial to the left nipple)

- The superficial temporal artery in front of the tragus of the external ear.

The cardiovascular system 1

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The cardiovascular system 1

The cardiovascular system includes the heart and the blood vessels.

THE HEART: (Fig. 19)

- The heart is a hollow muscular organ present in the thoracic cavity between the two lungs. It is conical in shape. Its apex is located in the 5^th left intercostal space (9 cm from the middle line) just below the left nipple.

- The heart consists of 4 chambers: two atria and two ventricles.

- On the external surface of the heart, the atria are separated from the ventricles by a groove known as the atrioventricular groove which lodges the coronary arteries that supply the heart Internally, the two atria are separated.

by the interatrial septum while the two ventricles are separated by the interventricular septum.

The heart could be divided into two halves which, are completely separate from each other. The right half consists of the right atrium and the right ventricle. The left half consists of the left atrium and left ventricle. The

right half of the heart contains deoxygenated (impure) blood while left half contains the oxygenated (pure) blood.

The right Mr’mm (Fig. 20) receives blood from the superior vena cava (which carries deoxygenated blood from the upper half of the body) and the inferior vena cave (which carries the deoxygenated blood from the lower half of the body).

It opens into the right ventricle by an opening guarded by a valve formed of three cusps known as the tricuspid valve which permits the flow of blood in one direction from the right atrium to the right ventricle.

The left atrium (Fig. 2r) receives the four pulmonary veins which carry the oxygenated (pure) blood from the lungs to the heart.

It opens into the left ventricle by an opening guarded by a

valve formed of two cusps, known as the mitral valve which permits the flow of blood in one direction from the left atrium to the left ventricle.

The right ventricle (Fig. 20) pumps the blood into the pulmonary trunk which communicates with the right ventricle by and opening (pulmonary opening) guarded by 3 semilunar cusps that allows the blood to flow in one

direction from the right-ventricle to the pulmonary trunk which carries the impure blood to the lungs.

- The left ventricle (Fig. 20) pumps the blood into the ascending aorta through the aortic opening which is guarded by the aortic valve composed of 3 semilunar cusps. The valve permits the flow of pure blood in one direction from the left ventricle to the ascending aorta and then to all parts of the body.

- The wall of the atrium is thinner than that of the ventricle because the atrium pumps blood only to the ventricle while the wall of the ventricle is thicker because it pumps the blood to distant areas. Also the wall of the left ventricle is 3 times thicker than that of the right ventricle because it pumps blood to all parts of the body.

The internal aspect of the wall of both ventricles presents muscular processes called papillary muscles which are connected to the cusps of the atrioventricular valve (tricuspid or mitral valve) by chordae tendinae. The papillary muscles and the chordae tendinae prevent eversion of the cusps toward the atria during contraction of the ventricles.

The Blood Vessels:

The blood vessels include arteries, veins and capillaries.

a) TSie arteries: carry the pure oxygenated blood from the heart to the different parts of the body (except the pulmonary artery which carries the impure deoxygenated blood from the heart to the lungs)

b) Tise veins: carry the impure deoxygenated blood from the different parts of the body to the heart (except the -34pulmonary veins which carry the pure oxygenated blood from the lungs to the heart).

c) The blood capillaries: are very minute blood vessels located in the tissues at the terminal part of an artery and the beginning of a vein connecting them together.

Ttae differences between an artery and a vela

No. \|	Artery	Vein
1	Carriers the blood from the heart to the tissues.	Carries blood from the tissues to the heart.
2	It transmits oxygenated blood (except the pulmonary artery).	It transmits deoxygenated blood (except the pulmonary veins).
3.	lis wall is thick as it contains a thick muscular laver	Its wall is thin.
4	Its wall contains an elastic layer so that it does not j collapse when cut.	Its wall does not contain an elastic layer so that it does collapse when cut.
5	It is not provided with valves	It is provided with valves

The respiratory system

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The respiratory system

The respiratory system consists of the nose, the pharynx, the larynx, thejrachea, the bronchi and the two lungs.

THE NOSE: (Fig. 16)

It consists of a bony part and a cartilaginous part. The nasal septum divides it into right and left halves. It opens anteriorly on the face by the anterior nares, and posteriorly into the nasopharynx by the posterior nares. Its lateral wall contains bony projections covered by mucous membrane called co.ochae…They are 3. in number, superior, middle, and inferior conchae.

The nasal cavity is lined by the nasal mucosa, whose upper part is concerned with the sensation of smell, while its

lower part is concerned with modulation of the temperature of the inspired air and filtering of foreign particles.

The paranasal sinuses are air filled extensions of the nasal cavity into the surrounding cranial bones. They are lined by mucous membrane. The secreted mucus passes to the nasal cavity through meatuses in its lateral walls.

The pharynx is a muscular tube that extends from the base of the skull above to the sixth cervical vertebra below. It lies behind the nasal cavity, the mouth cavity and the larynx. Its wall is composed of a muscle layer lined from the inside by mucous membrane. It is divided into 3 parts:

a) The nasopharynx: is the highest part which lies behind

the⁷ nose. It communicates anteriorly with the nose
through the posterior nares and on each side with the
middle ear through the openings of the right and left
auditory tubes (Eustchian tubes). Its roof contains the
pharyngeal tonsils which is a collection of lymphoid
tissue.

b) The oropharynx: which lies behind the oral cavity. It

communicatesanteriorly with the oral cavity. It is
common to both the alimentary and respiratory systems.
On its lateral walls lie the palatine tonsils.

cy The laryngopharynx: which lies behind the larynx. It communicates anteriorly with the inlet of the larynx.

The Larynx: (Fig. 17)

It is an air passage and it is also the organ of voice production. It connects the laryn go pharynx above with the

trachea below. It extends in the midline of the neck lying opposite the third, fourth, fifth, and sixth cervical vertebrae.

It is formed of a number of cartilages, which are connected together by ligaments, membranes, and muscles. It is lined by mucous membrane. The most important of its cartilages are the thyroid cartilage, the cricoid cartilage and the epiglottis. The epiglottis closes the inlet of the larynx during deglutition. It contains the two vocal cords which bound the glottis which is the narrowest part of the cavity of the larynx.

THE TRACHEA: (Fig. 17)

The trachea is a cartilaginous and membranous tube which conveys air into and out of the lungs. It begins at the lower end of the larynx at the level of the 6th cervical vertebra and terminates at the lower border of 4th throacic vertebra where it divides into the two main bronchi.

It is composed of about 20 cartilaginous C-shaped rings connected together with membranes. The) are incomplete posteriorly, where it is related to the oesophagus, being replaced by involuntary musc’e^ controlling its diameter.

The trachea is lined by mucous membrane provider with cilia which sweep the secretions to the outside.

THE TWO MAIN BRONCHI: (Fig. 17)

At the level of the lower border of the fourth thoracis vertebra, the trachea divides into the right and left ma^;i bronchi which are similar to the trachea in their structure.

a) The right main bronchus: it is shorter, wider, and more ertical than the left main bronchus.

b)The left main bronchus: it is longer, narrower, and more

oblique than the right main bronchus.

The LUNGS: (Fig. 18)

The lungs are the essential organs of respiration. They are normally light, soft, spong\ and elastic. During early life they are pink but during late life they are dark and mottled due to the entrapped carbon particles in the phagocytes.

Each lung has the shape of half a cone so that it has an apex, a base. 2 surfaces, and 3 borders.

The apex is directed upwards and lies above the I^s1 rib.

The base is concave, directed downwards and lies on the diaphragm.

The lateral surface is com ex and is related to the chest wall.

The medial surface is concave, related to the heart, and contains the hilum of the lung.

The hilum is the region where the corresponding bronchus, pulmonary artery, pulmonary veins, lymphatics, and nerves enter or leave the lung. These structures collectively form the root of the lung.

The lower border separates the base from the 2 surfaces, it is semilunar in shape.

The anterior border is sharper and shorter than the posterior border.

The posterior border is longer and thicker than the anterior border.

JOINTS

DAM — Fri, 10 Feb 2012 14:08:14 +0000

JOINTS

When two or more bones meet, an articulation or a joint is formed.

joints are classified according to functional and structural basis into three main types: fibrous, cartilaginous and synovial.

J. Fibrous Joints:

These do not permit any appreciable movement.

The bones are bound together (united) by intervening fibrous tissue. They are of two types.