This article was first published on April 10, 2015, and updated on August 15, 2018

A woman in the United States became the youngest recipient of a face transplant in 2017 at the age of 21.

Ms Katie Stubblefield, at 18, shot herself from below her chin using a hunting rifle when she attempted suicide due to numerous personal woes. She survived the shooting but much of her face was blasted off in her suicide attempt.

Ms Stubblefield, now 22, underwent a 31-hour long procedure last year that effectively replaced her full facial tissue. Her donor was Adrea Schneider, a 31-year-old woman who had died of a drug overdose.

The transplant involved her scalp, forehead, upper and lower eyelids, eye sockets, nose, upper cheeks, upper jaw and half of lower jaw, upper teeth, lower teeth, partial facial nerves, muscles and skin.

In 2016, a United States (US) volunteer firefighter whose face was burned off during a home fire rescue had successfully undergone the world's most extensive face transplant.

Patrick Hardison, 41, received a full scalp and face, including ears, nose, lips and upper and lower eyelids from 26-year-old David Rodebaugh, a BMX extreme bicycling enthusiast from Brooklyn who was pronounced brain dead after a cycling accident.

The procedure was done over 26 hours, by a 150-person medical team led by plastic surgeon Eduardo Rodriguez.

With advances in medical technology, what used to be considered unthinkable surgical operations have made headlines in recent years.

Computer scientist Valery Spiridonov, 30, who suffers from a rare muscle-wasting disease, volunteered in 2015 to be the first first person to undergo a controversial head transplant surgery devised by Italian physician Dr Sergio Canevero. Mr Spiridonov has since backed out of the surgery.

Here are some examples of unusual body parts transplants attempted.

1. Face transplants

In March 2012, Mr Richard Norris from US underwent one of the most extensive face transplants ever attempted in a 36-hour procedure involving 150 doctors and nurses at the University of Maryland Medical Centre.

Mr Norris, who had accidentally shot himself in the face with a shotgun in 1997, received the face of 21-year-old Joshua Aversano, who was killed in a traffic accident.

He also received two to three inches of Mr Aversano's hairline, forehead, eyebrows, nose, cheekbones, jaw, lips, teeth and tongue.

When Mr Aversano's sister Rebekah met Mr Norris for the first time, she took a stepped back and said, "This is the face I grew up with."

The world's first full-face transplant was conducted in 2010 on a Spanish man at the Vall d'Hebron hospital. During the 24-hour operation, doctors lifted an entire face, including jaw, nose, cheekbones, muscles, teeth and eyelids, and placed it mask-like onto his face.

Known only as Oscar, the patient was a farmer who had accidentally shot himself in the face. Several full face transplants have been carried out since.

The first partial face transplant was carried out in France in 2005.

In another path to facial reconstruction, a Chinese woman who lived for 25 years without a nose and mouth began treatment at a Shanghai hospital in April 2017..

Her nose and lips will be grown on her chest and transplanted on her face in a process that will take six months, said Xinhua news agency. By using her own cells, there is less chance that the facial organs will be rejected by her body.

2. Penis transplants

The first successful penis transplant was performed on a South African in his 20s who had suffered a botched circumcision.

It was a nine-hour operation, which took place in December 2014, at the Tygerberg Hospital in Cape Town.

Doctors said it was hard to convince the donor family to accede to the unusual request, but it is a procedure that will benefit hundreds of South Africans.

Each year, thousands of young South African men, mainly from the Xhosa tribe, undergo a traditional initiation into manhood that includes ritual circumcision. Many end up having to amputate their penises when the circumcision goes wrong.

An attempt at a penis transplant was made in China in 2006, but the patient requested for the part to be removed after it showed some swelling. The transplant also caused him and his wife psychological problems, he said.

In December 2015, doctors at the John Hopkins University announced that they were preparing to undergo a penis transplant in the US - a first of its kind in the country.

The operation is planned for a soldier who suffered genital injuries in a bomb blast in Afghanistan.

The 12-hour operation would involve the stitching of nerves and blood vessels which may eventually restore unirary function and the ability to have sex.

3. Womb transplants

Last year, a Swede, then 36, became the world's first woman to give birth after receiving a womb transplant. The donor is a friend who was in her 60s.

She was born without a womb, although her ovaries were intact.

The baby was born by Caesarean section at 31 weeks in September 2014, and weighed 1.7kg, according to the journal The Lancet. The woman was not named.

There have also been mother-to-daughter transplants: Two Swedish women were given uteri donated by their mothers in 2012.

The world's first womb transplant from a dead donor was done in Turkey in 2011. Derya Sert conceived a baby in 2013, but miscarried.

4. Replacement body parts

An eight-year-old American boy became the world's youngest recipient of a double-hand transplant in July 2015. Zion Harvey's hands and feet had previously been amputated following a major infection.

A team of 40 doctors, nurses and other staff from plastic and reconstructive surgery, orthopedic surgery, anesthesiology and radiology took 10 hours to pull off the pioneering surgery in July 2015, said doctors at The Children's Hospital of Philadelphia.

In Fujian last year, an extra nose was constructed out of a man's rib cartilage and implanted under the skin of his forehead to prepare for a transplant. The 22-year-old man damaged his nose in an accident in August 2012.

In Singapore, secondary school student Tan Li Xuan had one of her toes transplanted on to her half-severed thumb last year. The operation allows her to hold things with her right hand.

Three fingers of her hand were crushed by a sugar cane juicer when she was helping out at her father's drinks stall.

5. Six-organ transplants

Alannah Shevenell's oesophagus, liver, stomach, spleen, pancreas and small intestine were all replaced in 2011 when she was just eight.

The girl from Maine suffered multiple organ failures after a tumour metastasised, and had lost her ability to ingest or digest any food.

The operation was executed at Children's Hospital Boston, and all the organs came from one child donor. Alannah will have to take anti-rejection drugs all of her life, but has adapted well otherwise, reports said.

A Briton, Dawn Carter, also had a six-organ transplant in 2013 but she died 15 months after the operation, The Daily Mail said. The 53-year-old had her stomach, liver, kidney, colon, pancreas and intestine transplanted.