Living Body Assignment-1

Living Body Assignment

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The Digestive System

 The mouth- this is the start organ of the alimentary canal. It has many adaptations that

suit it to perform the function of breaking down food into smaller particles before

swallowing. There are four types of teeth that have different functions: incisors that cut

food, canines for slicing through food and biting, premolars and molars for grinding.

After breaking down the food, the tongue rolls it into boluses in the presence of saliva for

easy swallowing. Saliva is an important component that is secreted by the sublingual,

submandibular and the parotid glands mainly (Berkovitz, B.K., Holland, G.R. and

Moxham, B.J., 2016).

 The esophagus- food boluses enter the esophagus after the reflex swallowing action of

the pharyngeal muscles. The esophageal wall is composed of smooth muscles that are

organized in a circular and longitudinal manner. They contract and relax producing

waves that propel the food into the stomach through the cardiac sphincter.

 The stomach – this is a bag that holds food for some time while chemical digestion takes

place. Parietal cells secrete pepsin enzyme that breaks down proteins into amino acids.

Hydrochloric acid is also secreted by these cells creating an acidic environment for the

action of pepsin. Intrinsic factor binds vitamin B12 that will be absorbed later in the distal

ileum (Mahadevan, V., 2017).

 The liver- this is an accessory organ of the digestive system. It synthesizes bile juices that

are stored in the gall bladder. Besides these, it plays many other important roles in the

body such as glycogen synthesis, gluconeogenesis, fatty acid synthesis, protein synthesis

and breakdown and production of coagulation factors.

 The gall bladder stores and concentrates bile juices. Bile juice is composed of cholesterol,

water and salts such as sodium taurocholate. Bile juice is secreted via the bile duct into

the duodenum to aid in the digestion of lipids. Bile salts create an ionic environment

necessary for the formation of micelles that enhance digestion of lipids.

 The pancreas is also an accessory organ of the digestive system. It synthesizes digestive

juices that are secreted into the duodenum for digestion of food. Pancreatic juice contains

trypsin for protein digestion, lipase for lipid digestion and amylase for digestion of

carbohydrates.

 The small intestines has two parts: jejunum and ileum. This is the final site of digestion in

which food is broken down into individual constituent molecules and absorbed across the

villi. The small intestines are highly vascularized for efficient transport of substances.

After absorption, the food enters blood vessels and is transported to various body organs

for metabolism. Indigestible and undigested food then enters the colon.

 The colon is also referred to as the large intestines. No digestion occurs here. Absorption

of water is the major function of the colon. Absorption of vitamin K also occurs with the

help of gut microbiota. The wall of the colon is muscular with smooth muscles organized

circularly and longitudinally which upon contraction creates a wave that propels the

material into the rectum.

 The rectum provides a temporary store for undigested and indigestible material; feces

before evacuation through the anus.

The Circulatory System

 The left subclavian artery- this is a branch of the aortic arc that supplies blood to the left

upper limb. It divides into minor branches that supply individual compartments of the left

upper limb.

 The heart- this is the pump of the circulatory system. It is composed of ventricles and

atria. The right atrium receives deoxygenated blood from the entire body via the superior

and inferior vena cava. The blood enters the right ventricle and pumped to the lungs via

the pulmonary artery for oxygenation. From the lungs, blood returns back to then into the

left ventricle from which it is pumped to other parts of the body through the aorta. The

heart has its own vascular system, the coronary vessels, that nourish the cardiac tissues

(Lewis, T., 2015).

 The inferior vena cava- this vein receives blood from the mesenteric vessels and veins

from the renal system. This blood enters the right atrium and ventricle after which it is

pumped to the lungs for oxygenation.

 Capillaries- these are most minute blood vessels and form the site of gaseous exchange to

and from the body tissues. They have a thin wall composed mainly of the endothelium

that allows movement of oxygen from blood into the tissues, carbon IV oxide from

tissues into blood, end products of digestion from blood into tissues and metabolic

products from tissues into blood.

The Renal System

 The left kidney- kidneys are important excretory organs in the body. The nephron is the

basic unit of the kidney. Blood enters the glomerulus and undergoes filtration forming a

filtrate containing electrolytes, urea, glucose and water. Some of these undergo

reabsorption but the extent of this depends on their levels in blood. Urea is not

reabsorbed. The remaining substances go into the collecting duct and are excreted in

urine (Dirks-Naylor, A.J., 2016).

 The renal artery- this is a branch of the abdominal aorta. It divides into arterioles that

nourish the tissues of the kidney. Blood from the renal artery is filtered by the glomerulus

for removal of electrolytes and waste products.

 The ureter- forms the channel of connection between the kidney and urinary bladder.

After undergoing filtration, fluid from different nephrons drain into the ureter. It is a

hollow muscular channel that enters the bladder obliquely through sphincters to avoid

backflow.

 The urethra- this is the route of passage of urine from the urinary bladder during

micturition. It is longer in males where it is also part of the reproductive system but

shorter in females since it only serves as a passage of urine.

 The urinary bladder- this is a muscular organ capable of holding up to 150mL of urine. It

is innervated by the parasympathetic system that is stimulated once the bladder is full

eliciting the voiding reflex. It is also innervated by the sympathetic system that keeps the

sphincters intact to avoid involuntary evacuation. It has sphincters both at the entry of the

ureters and the start of the urethra that control the voiding process.

 The renal vein- filtered blood from the kidneys collects in the renal vein. This vessel

drains into the inferior vena cava and the blood is pumped to the heart then to the lungs

for oxygenation.

The Respiratory System

 Nose and mouth- these serve as initial passages of air during breathing. The nose is the

major route and it is adapted to conditioning air breathed in. it also has hairs that trap

particles that would affect the lungs. The mouth is used during strenuous activities or

when there is nasal congestion.

 Trachea- this is a hollow channel that conducts air from the nose and mouth into the

lungs. Its walls are composed of cartilage rings to keep it patent. It also has cilia that waft

dust and other particles to the pharynx for expulsion by coughing or through the sneezing

reflex.

 Lungs- these contain bronchioles and alveoli that are the sites for gaseous exchange.

Receive deoxygenated blood from the right ventricle via the pulmonary artery. After

oxygenation, the blood is transported back to the heart via the pulmonary vein.

 Diaphragm- this is a very important respiratory muscle. It contracts and relaxes

simultaneously to facilitate the process of inhalation and exhalation. This occurs in

concert with the action of the intercostal muscles.

 Alveoli- these are the basic units of the respiratory system. They are thin-walled and

highly vascularized. Oxygen from the alveoli diffuses into blood in the capillaries.

Carbon IV oxide present in blood diffuses into the alveoli for subsequent exhalation. This

exchange occurs across the alveolar membrane.

References List

Berkovitz, B.K., Holland, G.R. and Moxham, B.J., 2016. Oral anatomy, histology and

embryology. Elsevier.

Mahadevan, V., 2017. Anatomy of the stomach. Surgery-Oxford International Edition, 35 (11),

pp. 608-611

Lewis, T., 2015. Human Heart: Anatomy, Function & facts. Livescience. Techmedia Network, 7.

Dirks-Naylor, A.J., 2016. An active learning exercise to facilitate understanding of nephron

function: anatomy and physiology of renal transporters. Advances in physiology education, 40

(4), pp.469-471

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